SBA Communications (SBAC) 10-Q 7 May 18 2018 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 26, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Entity Registrant Name	SBA COMMUNICATIONS CORP
Entity Central Index Key	1,034,054
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		115,185,962
Trading Symbol	SBAC

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 109,350	$ 68,783
Restricted cash	28,372	32,924
Accounts receivable, net	101,103	90,673
Costs and estimated earnings in excess of billings on uncompleted contracts	13,039	17,437
Prepaid and other current assets	50,916	49,716
Total current assets	302,780	259,533
Property and equipment, net	2,803,478	2,812,346
Intangible assets, net	3,600,640	3,598,131
Other assets	698,184	650,195
Total assets	7,405,082	7,320,205
Current liabilities:
Accounts payable	29,554	33,334
Accrued expenses	60,223	69,862
Current maturities of long-term debt	20,000	20,000
Deferred revenue	93,407	97,969
Accrued interest	33,862	48,899
Other current liabilities	13,882	8,841
Total current liabilities	250,928	278,905
Long-term liabilities:
Long-term debt, net	9,363,686	9,290,686
Other long-term liabilities	378,709	349,728
Total long-term liabilities	9,742,395	9,640,414
Shareholders' deficit:
Preferred stock - par value $.01, 30,000 shares authorized, no shares issued or outstanding
Common stock - Class A, par value $.01, 400,000 shares authorized, 116,472 and 116,446 shares issued and outstanding at March 31, 2018 and December 31, 2017, respectively	1,165	1,164
Additional paid-in capital	2,184,989	2,167,470
Accumulated deficit	(4,395,286)	(4,388,288)
Accumulated other comprehensive loss, net	(379,109)	(379,460)
Total shareholders' deficit	(2,588,241)	(2,599,114)
Total liabilities and shareholders' deficit	$ 7,405,082	$ 7,320,205

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	30,000,000	30,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common Stock [Member]
Common stock - Class A, par value	$ 0.01	$ 0.01
Common stock - Class A, shares authorized	400,000,000	400,000,000
Common stock - Class A, shares issued	116,472,000	116,446,000
Common stock - Class A, shares outstanding	116,472,000	116,446,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Revenues:
Site leasing		$ 430,542	$ 397,550
Site development		27,760	25,813
Total revenues		458,302	423,363
Cost of revenues (exclusive of depreciation, accretion, and amortization shown below):
Cost of site leasing		92,817	89,382
Cost of site development		22,520	21,588
Selling, general, and administrative	[1]	36,049	34,223
Acquisition related adjustments and expenses		3,044	2,969
Asset impairment and decommission costs		8,506	8,351
Depreciation, accretion, and amortization		165,398	159,031
Total operating expenses		328,334	315,544
Operating income		129,968	107,819
Other income (expense):
Interest income		1,295	3,234
Interest expense		(88,923)	(77,602)
Non-cash interest expense		(733)	(705)
Amortization of deferred financing fees		(5,388)	(6,698)
Loss from extinguishment of debt, net		(645)
Other income, net		4,553	14,948
Total other expense		(89,841)	(66,823)
Income before provision for income taxes		40,127	40,996
Provision for income taxes		(8,582)	(3,398)
Net income		$ 31,545	$ 37,598
Net income per common share:
Basic		$ 0.27	$ 0.31
Diluted		$ 0.27	$ 0.31
Weighted average number of common shares
Basic		116,494	121,049
Diluted		118,293	121,734
[1]	Includes non-cash compensation of $9,893 and $8,826 for the three months ended March 31, 2018 and 2017, respectively.

Consolidated Statements of Ope5

Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Non-cash compensation expense	$ 10,410	$ 9,277
Selling, General And Administrative [Member]
Non-cash compensation expense	$ 9,893	$ 8,826

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 31,545	$ 37,598
Foreign currency translation adjustments	351	27,285
Comprehensive income	$ 31,896	$ 64,883

Consolidated Statement Of Share

Consolidated Statement Of Shareholders' Deficit - 3 months ended Mar. 31, 2018 - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]Class A Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive (Loss) Income, Net [Member]	Total
BALANCE at Dec. 31, 2017	$ 1,164	$ 2,167,470	$ (4,388,288)	$ (379,460)	$ (2,599,114)
BALANCE, Shares at Dec. 31, 2017	116,446
Net income (loss)			31,545		31,545
Common stock issued in connection with stock purchase/option plans	$ 3	6,883			6,886
Common stock issued in connection with stock purchase/option plans, Shares	264
Non-cash stock compensation		10,636			10,636
Repurchase and retirement of common stock	$ (2)		(38,543)		(38,545)
Repurchase and retirement of common stock, Shares	(238)
Foreign currency translation adjustments				351	351
BALANCE at Mar. 31, 2018	$ 1,165	$ 2,184,989	$ (4,395,286)	$ (379,109)	$ (2,588,241)
BALANCE, Shares at Mar. 31, 2018	116,472

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 31,545	$ 37,598
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, accretion, and amortization	165,398	159,031
Non-cash asset impairment and decommission costs	8,446	7,047
Non-cash compensation expense	10,410	9,277
Amortization of deferred financing fees	5,388	6,698
Gain on remeasurement of U.S. dollar denominated intercompany loans	(1,623)	(13,659)
Other non-cash items reflected in the Statements of Operations	1,296	35
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable and costs and estimated earnings in excess of billings on uncompleted contracts, net	(5,198)	1,444
Prepaid expenses and other assets	(9,277)	(4,777)
Accounts payable and accrued expenses	(14,336)	(3,899)
Accrued interest	(15,137)	(25,290)
Other liabilities	1,665	(1,199)
Net cash provided by operating activities	178,577	172,306
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions	(117,622)	(42,651)
Capital expenditures	(31,096)	(35,747)
Other investing activities	(2,879)	(5,879)
Net cash used in investing activities	(151,597)	(84,277)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings under Revolving Credit Facility	265,000
Repayments under Revolving Credit Facility	(70,000)	(110,000)
Repayment of Tower Securities	(755,000)
Proceeds from issuance of Tower Securities, net of fees	631,848
Repayment of Term Loans	(5,000)	(5,000)
Repurchase and retirement of common stock	(38,545)	(4,419)
Other financing activities	5,746	7,147
Net cash provided by (used in) financing activities	34,049	(112,272)
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	(504)	3,744
NET CHANGE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	60,525	(20,499)
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH:
Beginning of period	104,295	185,970
End of period	164,820	165,471
Cash paid during the period for:
Interest	104,011	102,875
Income taxes	2,148	$ 2,806
SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITIES:
Assets acquired through capital leases	$ 260

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2018
Basis of Presentation [Abstract]
Basis of Presentation	1. BASIS OF PRESENTATION The accompanying consolidated financial statements should be read in conjunction with the Annual Report on Form 10-K for the fiscal year ended December 31, 2017 for SBA Communications Corporation and its subsidiaries (the “Company”). These financial statements have been prepared in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X and, therefore, omit or condense certain footnotes and other information normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States. In the opinion of the Company’s management, all adjustments (consisting of normal recurring accruals) considered necessary for fair financial statement presentation have been made. The results of operations for an interim period may not give a true indication of the results for the year. Certain reclassifications have been made to prior year amounts or balances to conform to the presentation adopted in the current year. The preparation of financial statements requires management to make estimates and assumptions that affect the amounts reported in consolidated financial statements and accompanying notes. While the Company believes that such estimates are fair when considered in conjunction with the consolidated financial statements and accompanying notes, the actual amounts, when known, may vary from these estimates. Revenue Recognition and Accounts Receivable Revenue from site leasing is recognized on a straight-line basis over the current term of the related lease agreements, which are generally five to ten years. Receivables recorded related to the straight-lining of site leases are reflected in other assets on the Consolidated Balance Sheets. Rental amounts received in advance are recorded as deferred revenue on the Consolidated Balance Sheets. Revenues from site leasing represent 94% of the Company’s total revenues. Site development projects in which the Company performs consulting services include contracts on a fixed price basis . Site development projects are billed at contractual rates and revenue is recognized over time based on milestones achieved, which are determined based on costs incurred. Amounts billed in advance (collected or uncollected) are recorded as deferred revenue on the Consolidated Balance Sheets. Revenue from construction projects is recognized over time, determined by the percentage of cost incurred to date compared to management’s estimated total cost for each contract. This method is used because management considers total cost to be the best available measure of progress on the contracts. These amounts are based on estimates, and the uncertainty inherent in the estimates initially is reduced as work on the contracts nears completion. The asset “costs and estimated earnings in excess of billings on uncompleted contracts” represents costs incurred and revenues recognized in excess of amounts billed. The liability “billings in excess of costs and estimated earnings on uncompleted contracts,” included within other current liabilities on the Consolidated Balance Sheets, represents billings in excess of costs incurred and revenues recognized. Refer to Note 8 for further detail of costs and estimated earnings in excess of billings on uncompleted contracts. Provisions for estimated losses on uncompleted contracts are made in the period in which such losses are determined to be probable. The site development segment represents approximately 6% of the Company’s total revenues. The Company accounts for site development revenue in accordance with ASC 606, Revenue from Contracts with Customers, which the Company adopted on January 1, 2018 by applying the modified retrospective transition method. Payment terms do not result in any significant financing arrangements. Furthermore, these contracts do not typically include variable consideration; therefore, the transaction price that is recognized over time is generally the amount of the total contract. The cumulative effect of initially applying the new revenue standard had no impact on the Company’s financial results. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The adoption of the new standard will have no impact to net income on an ongoing basis. The accounts receivable balance was $101.1 million and $90.7 million as of March 31, 2018 and December 31, 2017 , respectively, of which $29.3 million and $20.8 million related to the site development segment as of March 31, 2018 and December 31, 2017 , respectively. The Company performs periodic credit evaluations of its customers. In addition, the Company monitors collections and payments from its customers and maintains a provision for estimated credit losses based upon historical experience, specific customer collection issues identified, and past due balances as determined based on contractual terms. Interest is charged on outstanding receivables from customers on a case by case basis in accordance with the terms of the respective contracts or agreements with those customers. Amounts determined to be uncollectible are written off against the allowance for doubtful accounts in the period in which uncollectibility is determined to be probable. Refer to Note 14 for further detail of the site development segment. Foreign Currency Translation All assets and liabilities of foreign subsidiaries that do not utilize the U.S. dollar as its functional currency are translated at period-end rates of exchange, while revenues and expenses are translated at monthly average rates of exchange prevailing during the period. Unrealized remeasurement gains and losses are reported as foreign currency translation adjustments through Accumulated Other Comprehensive Loss in the accompanying Consolidated Statement of Shareholders’ Deficit. For foreign subsidiaries where the U.S. dollar is the functional currency, monetary assets and liabilities of such subsidiaries, which are not denominated in U.S. dollars, are remeasured at exchange rates in effect at the balance sheet date, and revenues and expenses are remeasured at monthly average rates prevailing during the year. Unrealized translation gains and losses are reported as other income (expense), net in the Consolidated Statement of Operations. Intercompany Loans Subject to Remeasurement The Company has two wholly owned subsidiaries, Brazil Shareholder I, LLC, a Florida limited liability company, and SBA Torres Brasil, Limitada, a limitada existing under the laws of the Republic of Brazil, which have entered into intercompany loan agreements pursuant to which the entities may from time to time agree to lend/borrow amounts under the terms of each agreement. The first agreement entered into in November 2014 was for $750.0 million and was created to fund the acquisition of 1,641 towers in Brazil. The second agreement entered into in December 2017 was for $500.0 million and was created to fund the acquisition of 941 towers in Brazil. In accordance with Accounting Standards Codification (ASC) 830, the Company remeasures foreign denominated intercompany loans with the corresponding change in the balance being recorded in Other income (expense), net in the Consolidated Statement of Operations as settlement is anticipated or planned in the foreseeable future. For the three months ended March 31, 2018 and 2017 , the Company recorded a $1.6 million gain and a $13.7 million gain , respectively, on the remeasurement of intercompany loans due to changes in foreign exchange rates. As of March 31, 2018 , the aggregate amount outstanding under the two intercompany loan agreement s with the Company’s Brazilian subsidiary was $560.9 million. Recent Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU 2016-02, Leases. The standard requires lessees to recognize a right-of-use asset and a lease liability, initially measured at the present value of the lease payments for all leases with a term greater than 12 months. The accounting for lessors remains largely unchanged from existing guidance. This standard is effective for annual and interim periods beginning after December 15, 2018. Early adoption is permitted; however, the Company does not currently plan to early adopt. The Company has established a cross functional project plan and is assessing the impact of the standard on its consolidated financial statements. The Company expects this guidance to have a material impact on its consolidated balance sheet due to the recognition of right-of-use assets and lease liabilities for its ground leases. The Company does not expect adoption to have a significant impact on its lease classification or to have a material impact on its consolidated statement of operations. 

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Measurements [Abstract]
Fair Value Measurements	2. FAIR VALUE MEASUREMENTS Items Measured at Fair Value on a Recurring Basis — The Company’s earnout liabilities related to business combinat ions are measured at fair value on a recurring basis using Level 3 inputs and are recorded in Accrued expenses in the accompanying Consolidated Balance Sheets. Changes in estimate s are recorded in Acquisition related adjustments and expenses in the accompanying Consolidated Statement of Operations. The Company determines the fair value of earnouts (contingent consideration) and any subsequent changes in fair value using a discounted probability-weighted approach using Level 3 inputs. Level 3 valuations rely on unobservable inputs for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. The fair value of the earnouts is reviewed quarterly and is based on the payments the Company expects to make based on historical internal observations related to the anticipated performance of the underlying assets. The Company’s estimate of the fair value of its obligation contained in various acquisitions prior to January 1 , 2017 (adoption of ASU 2017-01) was $2.5 million as of March 31, 2018 and December 31, 2017 . The maximum potential obligation related to the performance targets for these various acquisitions was $3.1 million as of March 31, 2018 and December 31, 2017 . The maximum potential obligation related to the performance targets for acquisitions since January 1, 2017, which have not been recorded on the Company’s Consolidated Balance Sheet, w ere $15.5 million and $11.1 million as of March 31, 2018 and December 31, 2017 , respectively. The Company’s asset retirement obligations are measured at fair value on a recurring basis using Level 3 inputs and are recorded in Other long-term liabilities in the accompanying Consolidated Balance Sheets. The fair value of the asset retirement obligations is calculated using a discounted cash flow model. Items Measured at Fair Value on a Nonrecurring Basis — The Company’s long-lived assets and intangibles are measured at fair value on a nonrecurring basis using Level 3 inputs. The Company considers many factors and makes certain assumptions when making this assessment, including but not limited to: general market and economic conditions, historical operating results, geographic location, lease-up potential and expected timing of lease-up. The fair value of the long-lived assets and intangibles is calculated using a discounted cash flow model. Asset impairment and decommission costs for all periods presented and the related impaired assets primarily relate to the Company’s site leasing operating segment. The following summarizes the activity of asset impairment and decommission costs (in thousands):     For the three months  ended March 31,  2018 2017   Asset impairment (1) $ 5,855 $ 3,014  Write-off of carrying value of decommissioned towers 2,001 3,971  Other third party decommission costs 650 1,366  Total asset impairment and decommission costs $ 8,506 $ 8,351 (1) Represents impairment charges resulting from the Company’s regular analysis of whether the future cash flows from certain towers are adequate to recover the carrying value of the investment in those towers. Fair Value of Financial Instruments — The carrying values of cash and cash equivalents, accounts receivable, restricted cash, accounts payable, and short-term investments approximate their estimated fair values due to the short maturity of these instruments. Short-term investments consisted of $0.2 million in Treasury securities as of March 31, 2018 and December 31, 2017 . The Company’s estimate of the fair value of its held-to-maturity investments in treasury and corporate bonds, including current portion, are based primarily upon Level 1 reported market values. As of March 31, 2018 and December 31, 2017 , the carrying value and fair value of the held-to-maturity investments, including current portion, were $0.5 million. The current portion is recorded in Prepaid and other current assets in the accompanying Consolidated Balance Sheets, while held-to-maturity investments are recorded in Other assets. The Company determines fair value of its debt instruments utilizing various Level 2 sources including quoted prices and indicative quotes (non-binding quotes) from brokers that require judgment to interpret market information including implied credit spreads for similar borrowings on recent trades or bid/ask prices. The fair value of the Revolving Credit Facility is considered to approximate the carrying value because the interest payments are based on Eurodollar rates that reset month ly or more frequently . The Company does not believe its credit risk has changed materially from the date the applicable Eurodollar Rate was set for the Revolving Credit Facility ( 137.5 to 200.0 bas is points as of March 31, 2018 and 112.5 to 175.0 basis points as of the date of this filing). Refer to Note 10 for the fair values, principal balances, and carrying values of the Company’s debt instruments.

Restricted Cash

Restricted Cash	3 Months Ended
	Mar. 31, 2018
Restricted Cash [Abstract]
Restricted Cash	3. RESTRICTED CASH The cash, cash equivalents, and r estricted cash balances on the consolidated statement of cash flows consists of the following:     As of As of  March 31, 2018 December 31, 2017 Included on Balance Sheet   (in thousands)  Cash and cash equivalents $ 109,350 $ 68,783  Securitization escrow accounts 28,143 32,699 Restricted cash - current asset  Payment and performance bonds 229 225 Restricted cash - current asset  Surety bonds and workers compensation 2,596 2,588 Other assets - noncurrent  Cash held in escrow for acquisitions 24,502 — Other assets - noncurrent  Total cash, cash equivalents, and restricted cash $ 164,820 $ 104,295  Pursuant to the terms of the Tower Securities (see Note 10), the Company is required to establish a securitization escrow account, held by the indenture trustee, into which all rents and other sums due on the towers that secure the Tower Securities are directly deposited by the lessees. These restricted cash amounts are used to fund reserve accounts for the payment of (1) debt service costs, (2) ground rents, real estate and personal property taxes and insurance premiums related to towers, (3) trustee and servicing expenses, and (4) management fees. The restricted cash in the securitization escrow account in excess of required reserve balances is subsequently released to the Borrowers (as defined in Note 10) monthly, provided that the Borrowers are in compliance with their debt service coverage ratio and that no event of default has occurred. All monies held by the indenture trustee are classified as restricted cash on the Company’s Consolidated Balance Sheets. Payment and performance bonds relate primarily to collateral requirements fo r tower construction currently in process by the Company. Cash is pledged as collateral related to surety bonds issued for the benefit of the Company or its affiliates in the ordinary course of business and primarily related to the Company’s tower removal obligations. As of March 31, 2018 and December 31, 2017 , the Company had $39.6 million and $39.5 million in surety, payment and performance bonds, respectively . As of March 31, 2018 and December 31, 2017 , no collateral was required to be posted. The Company periodically evaluates the collateral posted for its bonds to ensure that it meets the minimum requirements. As of March 31, 2018 and December 31, 2017 , the Company had also pledged $2.5 million as collateral related to its workers compensation policy. During the quarter ended March 31, 2018, the Company placed $24.5 million into escrow accounts in anticipation of pending acquisitions. These amounts are designated for use in the acquisition of towers and their use is restricted for this activity. Should the acquisitions not be consummated and the Company is not in breach of the purchase and sale agreement, the funds would be returned back to the Company without penalty. Subsequent to March 31, 2018 , the Company closed on one of the pending acquisitions and $10 .0 million of the escrow deposits were transferred from th e escrow account to the seller.

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets and Other Assets	3 Months Ended
	Mar. 31, 2018
Prepaid Expenses and Other Current Assets and Other Assets [Abstract]
Prepaid Expenses and Other Current Assets and Other Assets	4. PREPAID EXPENSES AND OTHER CURRENT ASSETS AND OTHER ASSETS The Company’s prepaid expenses and other current assets are comprised of the following:     As of As of  March 31, 2018 December 31, 2017   (in thousands)  Prepaid ground rent $ 31,257 $ 32,505  Other 19,659 17,211  Total prepaid expenses and other current assets $ 50,916 $ 49,716      The Company’s other assets are comprised of the following:     As of As of  March 31, 2018 December 31, 2017   (in thousands)  Prepaid ground rent $ 230,327 $ 220,493  Straight-line rent receivable 318,841 313,650  Deferred lease costs, net 27,519 27,703  Cash held in escrow for acquisitions 24,502 —  Other 96,995 88,349  Total other assets $ 698,184 $ 650,195  

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2018
Acquisitions [Abstract]
Acquisitions	5. ACQUISITIONS The fo llowing table summarizes the Company’s cash acquisition capital expenditures:     For the three months  ended March 31,  2018 2017   (in thousands)  Acquisitions of towers and related intangible assets $ 108,355 $ 31,147  Land buyouts and other assets (1) 9,267 11,504  Total cash acquisition capital expenditures $ 117,622 $ 42,651  (1) In addition, the Company paid $6.6 million and $2.7 million for ground lease extensions and term easements on land underlying the Company’s towers during the three months ended March 31, 2018 and 2017 , respectively. The Company recorded these amounts in prepaid rent on its Consolidated Balance Sheets . For acquisitions which qualify as asset acquisitions, the aggregate purchase price is allocated on a relative fair value basis to towers and related intangible assets . The fair values of these net assets acquired are based on management’s estimates and assumptions, as well as other information compiled by management, including valuations that utilize customary valuation procedures and techniques. The fair value estimates are based on available historical information and on future expectations and assumptions deemed reasonable by management at the time. If the actual results differ from the estimates and judgments used in these fair values, the amounts recorded in the consolidated financial statements could be subject to a possible impairment of the intangible assets, or require acceleration of the amortization expense of intangible assets in subsequent periods. For business c ombinations, the estimates of the fair value of the assets acquired and liabilities assumed at the date of an acquisition are subject to adjustment during the measurement period (up to one year from the particular acquisition date). During the measurement period, the Company will adjust assets and/or liabilities if new information is obtained about facts and circumstances that existed as of the acquisition date that, if known, would have re sulted in a revised estimated value of those assets and/or liabilities as of that date. As of March 31, 2018, there were no purchase price allocations that were preliminary. During the three months ended March 31, 2018 , the Company acquired 334 completed towers and related assets and liabilities consisting of $23.2 million of property and equipment, $101.3 million of intangible assets, and $16.2 million of working capital adjustments. All acquisitions in the quarter ended March 31, 2018 were accounted for as asset acquisitions. Subsequent to March 31, 2018 , the Company acquired 190 towers and related assets for $119.5 million in cash .

Intangible Assets, Net

Intangible Assets, Net	3 Months Ended
	Mar. 31, 2018
Intangible Assets, Net [Abstract]
Intangible Assets, Net	6. INTANGIBLE ASSETS, NET The following table provides the gross and net carrying amounts for each major class of intangible assets:     As of March 31, 2018 As of December 31, 2017  Gross carrying Accumulated Net book Gross carrying Accumulated Net book  amount amortization value amount amortization value   (in thousands)  Current contract intangibles $ 4,425,965 $ (1,746,160) $ 2,679,805 $ 4,355,171 $ (1,673,270) $ 2,681,901  Network location intangibles 1,649,246 (728,411) 920,835 1,617,441 (701,211) 916,230  Intangible assets, net $ 6,075,211 $ (2,474,571) $ 3,600,640 $ 5,972,612 $ (2,374,481) $ 3,598,131  All intangible assets noted above are included in t he Company’s site leasing segment. The Company amortizes its intangible assets using the straight-line method over 15 years. Amortization expense relating to the intangible assets above was $100.3 million and $94.9 million for the three months ended March 31, 2018 and 2017 , respectively .

Property and Equipment, Net

Property and Equipment, Net	3 Months Ended
	Mar. 31, 2018
Property and Equipment, Net [Abstract]
Property and Equipment, Net	7. PROPERTY AND EQUIPMENT, NET Property and equipment, net (including vehicle s held under capital lea ses) consists of the following:    As of As of  March 31, 2018 December 31, 2017   (in thousands)  Towers and related components $ 4,817,195 $ 4,772,807  Construction-in-process 35,175 34,689  Furniture, equipment, and vehicles 53,485 53,260  Land, buildings, and improvements 638,609 630,370  Total property and equipment 5,544,464 5,491,126  Less: accumulated depreciation (2,740,986) (2,678,780)  Property and equipment, net $ 2,803,478 $ 2,812,346  Construction-in-process represents costs incurred related to towers that are under development and will be used in the Company’s operations. Depreciation expense was $65.0 million and $64.1 million for the three months ended March 31, 2018 and 2017 , respectively. At March 31, 2018 and December 31, 2017 , non-cash capital expenditures that are included in accounts payable and accrued expenses were $10.4 million and $12.4 million, respectively .

Costs and Estimated Earnings on

Costs and Estimated Earnings on Uncompleted Contracts	3 Months Ended
	Mar. 31, 2018
Costs and Estimated Earnings on Uncompleted Contracts [Abstract]
Costs and Estimated Earnings on Uncompleted Contracts	8. COSTS AND ESTIMATED EARNINGS ON UNCOMPLETED CONTRACTS Costs and estimated earnings on uncompleted contracts consist of the following:     As of As of  March 31, 2018 December 31, 2017   (in thousands)  Costs incurred on uncompleted contracts $ 33,232 $ 31,404  Estimated earnings 11,836 10,541  Billings to date (32,495) (24,771)  $ 12,573 $ 17,174  These amounts are included in the accompanying Consolidated Balance Sheets under the following captions:     As of As of  March 31, 2018 December 31, 2017   (in thousands)  Costs and estimated earnings in excess of billings on uncompleted contracts $ 13,039 $ 17,437  Billings in excess of costs and estimated earnings on  uncompleted contracts (included in Other current liabilities) (466) (263)  $ 12,573 $ 17,174  A t March 31, 2018 and December 31, 2017 , eight customers comprised 87.4% and 87.9% of the costs and estimated earnings in excess of billings on uncompleted contracts, net of billings in excess of costs and estimated earnings , respectively.

Accrued Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2018
Accrued Expenses [Abstract]
Accrued Expenses	 9. ACCRUED EXPENSES The Company’s accrued expenses are comprised of the following:    As of As of  March 31, 2018 December 31, 2017   (in thousands)  Accrued earnouts on business combinations $ 2,503 $ 2,470  Salaries and benefits 5,755 13,506  Real estate and property taxes 6,900 7,125  Non-cash capital expenditures 10,352 12,408  Other 34,713 34,353  Total accrued expenses $ 60,223 $ 69,862  

Debt

Debt	3 Months Ended
	Mar. 31, 2018
Debt [Abstract]
Debt	10. DEBT The principal values, fair values, and carrying values of debt consist of the following (in thousands):     As of As of  March 31, 2018 December 31, 2017  Maturity Date Principal Balance Fair Value Carrying Value Principal Balance Fair Value Carrying Value  2014 Senior Notes Jul. 15, 2022 $ 750,000 $ 753,750 $ 739,617 $ 750,000 $ 770,625 $ 739,079  2016 Senior Notes Sep. 1, 2024 1,100,000 1,075,250 1,081,857 1,100,000 1,127,500 1,081,262  2017 Senior Notes Oct. 1, 2022 750,000 718,125 741,846 750,000 750,938 741,437  2013-1C Tower Securities Apr. 10, 2018 — — — 425,000 423,853 424,482  2013-2C Tower Securities Apr. 11, 2023 575,000 568,071 568,881 575,000 578,433 568,609  2013-1D Tower Securities Ap. 10, 2018 — — — 330,000 330,145 329,585  2014-1C Tower Securities Oct. 8, 2019 920,000 910,395 915,621 920,000 915,216 914,929  2014-2C Tower Securities Oct. 8, 2024 620,000 607,067 613,672 620,000 620,942 613,461  2015-1C Tower Securities Oct. 8, 2020 500,000 492,260 494,028 500,000 496,840 493,474  2016-1C Tower Securities Jul. 9, 2021 700,000 691,726 693,578 700,000 691,166 693,118  2017-1C Tower Securities Apr. 11, 2022 760,000 740,992 751,548 760,000 751,404 751,076  2018-1C Tower Securities Mar. 9, 2023 640,000 638,650 631,939 — — —  Revolving Credit Facility Feb. 5, 2020 235,000 235,000 235,000 40,000 40,000 40,000  2014 Term Loan Mar. 24, 2021 1,443,750 1,447,359 1,436,207 1,447,500 1,451,119 1,439,373  2015 Term Loan Jun. 10, 2022 486,250 486,250 479,892 487,500 488,109 480,801  Total debt $ 9,480,000 $ 9,364,895 $ 9,383,686 $ 9,405,000 $ 9,436,290 $ 9,310,686  Less: current maturities of long-term debt (20,000) (20,000)  Total long-term debt, net of current maturities $ 9,363,686 $ 9,290,686  The table below reflects cash and non-cash interest expense amounts recognized by debt instrument for the periods presented:      For the three months ended March 31,  2018 2017  Cash Non-cash Cash Non-cash  Interest Interest Interest Interest   (in thousands)  2014 Senior Notes $ 9,141 $ 187 $ 9,141 $ 178  2016 Senior Notes 13,406 246 13,406 234  2017 Senior Notes 7,500 — — —  2012 Tower Securities — — 4,524 —  2013 Tower Securities 9,475 — 10,804 —  2014 Tower Securities 12,785 — 12,785 —  2015-1C Tower Securities 3,985 — 3,985 —  2016-1C Tower Securities 5,090 — 5,090 —  2017-1C Tower Securities 6,085 — — —  2018-1C Tower Securities 1,362 — — —  Revolving Credit Facility 1,601 — 2,770 —  2014 Term Loan 13,947 131 11,284 128  2015 Term Loan 4,697 169 3,800 165  Other (151) — 13 —  Total $ 88,923 $ 733 $ 77,602 $ 705  Senior Credit Agreement On April 11, 2018, the Company amended and restated its Senior Credit Agreement to (1) issue a new $2.4 billion Term Loan, (2) increase the total commitments under the Revolving Credit Facility from $1.0 billion to $1.25 billion, ( 3 ) extend the maturity date of the Revolving Credit Facility to April 11, 2023 , ( 4 ) lower the applicable interest rate margins and commitm ent fees under the Revolving Credit Facility, and ( 5 ) amend certain other terms and conditions und er the Senior Credit Agreement. The proceeds from the new Term Loan were used to repay the outstanding balance on the 2014 Term Loan, 2015 Term Loan, and Revolving Credit Facility and for general corporate purposes. This transaction was accounted for as an extinguishment of the 2014 Term Loan and 2015 Term Loan. Revolving Credit Facility under the Senior Credit Agreement As amended, the Revolving Credit Facility consists of a revolving loan under which up to $1.25 billion aggregate principal amount may be borrowed, repaid and redrawn, based upon specific financial ratios and subject to the satisfaction of other customary conditions to borrowing. Amounts borrowed under the Revolving Credit Facility accrue interest, at SBA Senior Finance II’s election, at either (i) the Eurodollar Rate plus a margin that ranges from 112.5 basis points to 175.0 basis points or (ii) the Base Rate plus a margin that ranges from 12.5 basis points to 75.0 basis points, in each case based on the ratio of Consolidated Net Debt to Annualized Borrower EBITDA , calculated in accordance with the Senior Credit Agreement. In addition, SBA Senior Finance II is required to pay a commitment fee of between 0.20% and 0.25% per annum on the amount of unused commitment. If not earlier terminated by SBA Senior Finance II, the Revolving Credit Facility will terminate on, and SBA Senior Finance II will repay all amounts outstanding on or before, April 11, 2023 . The proceeds available under the Revolving Credit Facility may be used for general corporate purposes. Prior to the amendment, a mounts borrowed under the Revolving Credit Facility accrued interest, at SBA Senior Finance II’s election, at either (i) the Eurodollar Rate plus a margin that range d from 137.5 basis points to 200.0 basis points or (ii) the Base Rate plus a margin that range d from 37.5 basis points to 100.0 basis points, in each case based on the ratio of Consolidated Total Debt to Annualized Borrower EBITDA, calculated in accordance wi th the Senior Credit Agreement. During the three months ended March 31, 2018 , the Company borrowed $265.0 million and repaid $70.0 million of the outstanding balance under the Revolving Credit Facility. As of March 31, 2018 , the balance outstanding under the Revolving Credit Facility was $235.0 million and accrued interest at 3.74% per annum. In addition, SBA Senior Finance II wa s required to pay a commitment fee of 0.25% per annum on the amount of unused commitment. As of March 31, 2018 , SBA Senior Finance II was in compliance with the financial covenants contained in the Senior Credit Agreement. Subsequent to March 31, 2018 , the Company borrowed an additional $200.0 million and repaid $335.0 million of the outstanding balance under the Revolving Credit Facility. As of the date of this filing , $ 100.0 million was outstanding under the Revolving Credit Facility and was accruing interest at 3.26% per annum . Term Loans under the Senior Credit Agreement 2014 Term Loan The 2014 Term Loan consist ed of a senior secured term loan with an initial aggregate principal amount of $1.5 billion that was scheduled to mature on March 24, 2021 . The 2014 Term Loan accrued interest, at SBA Senior Finance II’s election at either the Base Rate plus 125 basis points (with a zero Base Rate floor) or the Eurodollar Rate plus 225 basis points (with a zero Eurodollar Rate floor). The 2014 Term Loan was originally issued at 99.75% of par value. As of March 31, 2018 , the 2014 Term Loan was accruing interest at 3.99% per annum. Principal payments on the 2014 Term Loan commenced on September 30, 2014 and we re being made in quarterly installments on the last day of each March, June, September, and December in an amount equal to $3.8 million. The Company incurred deferred financing fees of approximately $14.1 million in relation to this transaction, which we re being amortized through the maturity date. During the three months ended March 31, 2018 , the Company repaid $ 3.8 million of principal on the 2014 Term Loan. As of March 31, 2018 , the 2014 Term Loan had a principal balance of $1,443.8 m illion. On April 11, 2018, the Company repaid the entire $1,443.8 million outstanding principal balance of the 2014 Term Loan. In connection with the prepayment, the Company expensed $5.8 million of net deferred financing fees and $1.7 million of discount related to the debt. 2015 Term Loan The 2015 Term Loan consist ed of a senior secured term loan with an initial aggregate principal amount of $500.0 million that was scheduled to mature on June 10, 2022 . The 2015 Term Loan accrued interest, at SBA Senior Finance II’s election at either the Base Rate plus 125 basis points (with a zero Base Rate floor) or the Eurodollar Rate plus 225 basis points (with a zero Eurodollar Rate floor). The 2015 Term Loan was originally issued at 99.0% of par value. As of March 31, 2018 , the 2015 Term Loan was accruing interest at 3.99% per annum. Principal payments on the 2015 Term Loan commenced on September 30, 2015 and we re being made in quarterly installments on the last day of each March, June, September, and December in an amount equal to $1.3 million. The Company incurred deferred financing fees of approximately $5.5 million in relation to this transaction, which we re being amortized through the maturity date. During the three months ended March 31, 2018 , the Company repaid $1.3 millio n of principal on the 2015 Term Loan. As of March 31, 2018 , the 2015 Term Loan had a principal balance of $486.3 million. On April 11, 2018, the Company repaid the entire $486.3 million outstanding principal balance of the 2015 Term Loan. In connection with the prepayment, the Company expensed $3.2 million of net deferred financing fees and $3.1 million of discount related to the debt. 2018 Term Loan On April 11, 2018, the Company, through its wholly owned subsidiary, SBA Senior Finance II LLC, obtained a new term loan (the “2018 Term Loan ” ) under the amended and restated Senior Credit Agreement. The 201 8 Term Loan consist s of a senior secured term loan with an initial aggregate principal amount of $2.4 b illion that mature s on April 11, 2025 . The 2018 Term Loan accrues interest, at SBA Senior Finance II’s election at either the Base Rate plus 100 basis points (with a zero Base Rate floor) or the Eurodollar Rate plus 200 basis points (with a zero Eurodollar Rate floor). The 201 8 Term Loan was issued at 99.75% of par value. Principal payments on the 201 8 Term Loan commence on September 30, 2018 and will be made in quarterly installments on the last day of each March, June, September, and December in an amount equal to $6.0 million. The Company incurred deferred financing fees of approximately $15.9 million to date in relation to this transaction, which are being amortized through the maturity date. The proceeds from the 2018 Term Loan were used ( 1) to retire the outstanding $1.93 billion in aggregate principal amount of the existing term loans, (2) to pay down the existing outstanding balance under the Revolving Credit Facility, and (3) for general corporate purposes. Secured Tower Revenue Securities 2013 Tower Securities On April 18, 2013, the Company, through a New York common law trust ( the “ Trust ”) , issued $425.0 million of 2.240% Secured Tower Revenue Securities Series 2013-1C, which ha d an anticipated repayment date of April 10, 2018 and a final maturity date of April 9, 2043 (the “2013-1C Tower Securities”), $575.0 million of 3.722% Secured Tower Revenue Securities Series 2013-2C, which have an anticipated repayment date of April 11, 2023 and a final maturity date of April 9, 2048 (the “2013-2C Tower Securities”), and $330.0 million of 3.598% Secured Tower Revenue Securities Series 2013-1D, which ha d an anticipated repayment date of April 10, 2018 and a final maturity date of April 9, 2043 (the “2013-1D Tower Securities”) (collectively the “2013 Tower Securities”). The aggregate $1.33 billion of 2013 Tower Securities ha d a blended interest rate of 3.218% per annum, payable monthly. The Company incurred deferred financing fees of $25.5 million in relation to this transaction, which we re being amortized through the anticipated repayment date of each of the 2013 Tower Securities. On March 9, 2018, t he Company repaid the entire aggregate principal amount of the 2013-1C Tower Securities and 2013-1D Tower Securities in connection with the issuance of the 2018-1C Tower Securities (as defined below). The sole asset of the Trust consists of a non-recourse mortgage loan made in favor of those entities that are borrowers on the mortgage loan (the “Borrowers”). 2014 Tower Securities On October 15, 2014, the Company, through the Trust, issued $920.0 million of 2.898% Secured Tower Revenue Securities Series 2014-1C, which have an anticipated repayment date of October 8, 2019 and a final maturity date of October 11, 2044 (the “2014-1C Tower Securities”) and $620.0 million of 3.869% Secured Tower Revenue Securities Series 2014-2C, which have an anticipated repayment date of October 8, 2024 and a final maturity date of October 8, 2049 (the “2014-2C Tower Securities”) (collectively the “2014 Tower Securities”). The aggregate $1.54 billion of 2014 Tower Securities have a blended interest rate of 3.289% per annum, payable monthly. The Company incurred deferred financing fees of $22.5 million in relation to this transaction, which are being amortized through the anticipated repayment date of each of the 2014 Tower Securities. 2015-1C Tower Securities On October 14, 2015, the Company, through the Trust, issued $500.0 million of Secured Tower Revenue Securities Series 2015-1C, which have an anticipated repayment date of October 8, 2020 and a final maturity date of October 10, 2045 (the “2015-1C Tower Securities”). The fixed interest rate of the 2015-1C Tower Securities is 3.156% per annum, payable monthly. The Company incurred deferred financing fees of $11.2 million in relation to this transaction, which are being amortized through the anticipated repayment date of the 2015-1C Tower Securities. 2016-1C Tower Securities On July 7, 2016, the Company, through the Trust, issued $700.0 million of Secured Tower Revenue Securities Series 2016-1C, which have an anticipated repayment date of July 9, 2021 and a final maturity date of July 10, 2046 (the “2016-1C Tower Securities”). The fixed interest rate of the 2016-1C Tower Securities is 2.877% per annum, payable monthly. Net proceeds from this offering were used to prepay the full $550.0 million outstanding on the 2010-2C Tower Securities and for general corporate purposes. The Company incurred deferred financing fees of $9.5 million in relation to this transaction, which are being amortized through the anticipated repayment date of the 2016-1C Tower Securities. 2017-1C Tower Securities On April 17, 2017, the Company, through the Trust, issued $760.0 million of Secured Tower Revenue Securities Series 2017-1C, which have an anticipated repayment date of April 11, 2022 and a final maturity date of April 9, 2047 (the “2017-1C Tower Securities”). The fixed interest rate on the 2017-1C Tower Securities is 3.168% per annum, payable monthly. Net proceeds from this offering were used to prepay the entire $610.0 million aggregate principal amount, as well as accrued and unpaid interest, of the 2012-1C Tower Securities and for general cor porate purposes. The Company incurred deferred financing fees of $10.2 million in relation to this transaction, which are being amortized through the anticipated repayment date of the 2017-1C Tower Securities. In addition, to satisfy certain risk retention requirements of Regulation RR promulgated under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), SBA Guarantor, LLC, a wholly owned subsidiary , purchased $40.0 million of Secured Tower Revenue Securities Series 2017-1R issued by the Trust, which have an anticipated repayment date of April 11, 2022 and a final maturity date of April 9, 2047 (the “2017-1R Tower Securities”). The fixed interest rate on the 2017-1R Tower Securities is 4.459% per annum, payable monthly. Principal and interest payments made on the 2017-1R Tower Securities eliminate in consolidation. 2018-1C Tower Securities On March 9, 2018, the Company, through the Trust, issued $640.0 million of Secured Tower Revenue Securities Series 2018-1C, which have an anticipated repayment date of March 9, 2023 and a final maturity date of March 9, 2048 (the “2018-1C Tower Securities”). The fixed interest rate on the 2018-1C Tower Securities is 3.448% per annum, payable monthly. Net proceeds from this offering, in combination with borrowings under the Revolving Credit Facility, were used to repay the entire aggregate principal amount of the 2013-1C Tower Securities ( $425.0 million) and 2013-1D Tower Securities ( $330.0 million), as well as accrued and unpaid interest. The Company incurred deferred financing fees of $8.2 million in relation to this transaction, which are being amortized through the anticipated repayment date of the 2018-1C Tower Securities. In addition, to satisfy certain risk retention requirements of Regulation RR promulgated under the Exchange Act, SBA Guarantor, LLC, a wholly owned subsidiary, purchased $33.7 million of Secured Tower Revenue Securities Series 2018-1R issued by the Trust. These securities have an anticipated repayment date of March 9, 2023 and a final maturity date of March 9, 2048 (the “2018-1R Tower Securities”). The fixed interest rate on the 2018-1R Tower Securities is 4.949% per annum, payable monthly. Principal and interest payments made on the 2018-1R Tower Securities eliminate in consolidation. In connection with the issuance of the 2018-1C Tower Securities, the non-recourse mortgage loan was increased by $673.7 million (but decreased by a net of $81.3 million after giving effect to prepayment of the loan components relating to the 2013-1C Tower Securities and 2013-1D Tower Securities). The new loan, after eliminating the risk retention securities, accrues interest at the same rate as the 2018-1C Tower Securities and is subject to all other material terms of the existing mortgage loan, including collateral and interest rate after the anticipated repayment date. Debt Covenants As of March 31, 2018 , the Borrowers met the debt service coverage ratio required by the mortgage loan agreement and were in compliance with all other covenants as set forth in the agreement. Senior Notes 2014 Senior Notes On July 1, 2014, the Company issued $750.0 million of unsecured senior notes due July 15, 2022 (the “2014 Senior Notes”). The 2014 Senior Notes accrue interest at a rate of 4.875% per annum and were issued at 99.178% of par value. Interest on the 2014 Senior Notes is due semi-annually on January 15 and July 15 of each year. The Company incurred deferred financing fees of $11.6 million in relation to this transaction, which are being amort ized through the maturity date. The 2014 Senior Notes are subject to redemption in whole or in part on or after July 15, 2017 at the redemption prices set forth in the indenture agreement plus accrued and unpaid interest. The Company may redeem the 2014 Senior Notes during the twelve-month period beginning on the following dates at th e following redemption prices: July 15, 2017 at 103.656% , July 15, 2018 at 102.438% , July 15, 2019 at 101.219% , or July 15, 2020 until maturity at 100.000% , of the principal amount of the 2014 Senior Notes to be redeemed on the redemption date plus accrued and unpaid interest. 2016 Senior Notes On August 15, 2016, the Company issued $1.1 billion of unsecured senior notes due September 1, 2024 (the “2016 Senior Notes”). The 2016 Senior Notes accrue interest at a rate of 4.875% per annum and were issued at 99.178% of par value. Interest on the 2016 Senior Notes is due semi-annually on March 1 and September 1 of each year, beginning on March 1, 2017. The Company incurred deferred financing fees of $12.8 million in relation to this transaction, which are being amortized through the maturity date. Net proceeds from this offering and cash on hand were used to redeem $800.0 million, the aggregate principal amount outstanding, of Telecommunications’ 5.75% Senior Notes and $250.0 million of the Company’s 5.625% Senior Notes and pay the associated call premiums. The 2016 Senior Notes are subject to redemption in whole or in part on or after September 1, 2019 at the redemption prices set forth in the indenture agreement plus accrued and unpaid interest. Prior to September 1, 2019, the Company may at its option redeem up to 35% of the aggregate principal amount of the 2016 Senior Notes originally issued at a redemption price of 104.875% of the principal amount of the 2016 Senior Notes to be redeemed on the redemption date plus accrued and unpaid interest with the net proceeds of certain equity offerings. The Company may redeem the 2016 Senior Notes during the twelve-month period beginning on the following dates at th e following redemption prices: September 1, 2019 at 103.656% , September 1, 2020 at 102.438% , September 1, 2021 at 101.219% , or September 1, 2022 until maturity at 100.000% , of the principal amount of the 2016 Senior Notes to be redeemed on the redemption date plus accrued and unpaid interest. 2017 S enior Notes On October 13, 2017, the Company issued $750.0 million of unsecur ed senior notes due October 1, 2022 (the “2017 Senior Notes”). The 2017 Senior Notes accrue interest at a rate of 4.0% per annum. Interest on the 2017 Senior Notes is due semi-annually on April 1 and October 1 of each year, beginning on April 1, 2018. The Company incurred deferred financing fees of $8.9 million in relation to this transaction, which are being amortized through the maturity date. Net proceeds from this offering were used to re pay $460.0 million outstanding under the Revolving Credit Facility and for general corporate purposes . The 2017 Senior Notes are subject to redemption in whole or in part on or after October 1, 2019 at the redemption prices set forth in the indenture agreement plus accrued and unpaid interest. Prior to October 1, 2020, the Company may, at the Company’s option, redeem up to 35% of the aggregate principal amount of the 2017 Senior Notes originally issued at a redemption price of 104.000% of the principal amount of the 2017 Senior Notes to be redeemed on the redemption date plus accrued and unpaid interest with the net proceeds of certain equity offerings. The Company ma y redeem the 2017 Senior Notes during the twelve-month period beginning on the following dates at the following redemption prices: October 1, 2019 at 102.000% , October 1, 2020 at 101.000% , or October 1, 2021 until maturity at 100.000% , of the principal amount of the 2017 Senior Notes to be redeemed on the redemption date plus accrued and unpaid interest.

Shareholders' Equity

Shareholders' Equity	3 Months Ended
	Mar. 31, 2018
Shareholders' Equity [Abstract]
Shareholders' Equity	11. SHAREHOLDERS’ EQUITY Common Stock E quivalents The Company has potential common stock equivalents (see Note 12) related to its outstanding stock options and restricted stock units . These potential common stock equivalents were considered in the Company’s diluted earnings per share calculation (see Note 15). Stock Repurchases On February 16, 2018, the Company’s Boa rd of Directors authorized a $1.0 billion stock repurchase plan replacing the prior plan authorized on January 12, 2017 which had a remaining authorization of $150.0 million. This new plan authorizes the Company to purchase, from time to time, up to $1.0 billion of the outstanding Class A common stock through open market repurchases in compliance with Rule 10b-18 under the Exchange Act and/or in privately negotiated transactions at management’s discretion based on market and business conditions, applicable legal requirements and other factors. Shares repur chased will be retired. The plan has no time deadline and will continue until otherwise modified or terminated by the Company’s Board of Directors at any time in its sole discretion. During the three months ended March 31, 2018 , the Company repurchased 0.2 million shares of its Class A common stock under this plan for $38.5 million, at an average price per share of $161.60 . Shares repurchased were retired. Subsequent to March 31, 2018 , the Company repurchased 1.6 million shares of its Class A common stock for $261.5 million, at an average price per share of $164.82 . Shares repurchased were retired. As of the date of this filing , the Company had $700.0 million of authorization remaining under the current stock repurchase plan .

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2018
Stock-Based Compensation [Abstract]
Stock-Based Compensation	12. STOCK-BASED COMPENSATION Stock Options The Company records compensation expense for employee stock options based on the estimated fair value of the options on the date of grant using the Black-Scholes option-pricing model with the assumptions included in the table below. The Company uses a combination of historical data and historical volatility to establish the expected volatility , as well as to estimate the expected option life. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for the estimated life of the option. The following assumptions were used to estimate the fair value of options granted using the Black-Scholes option-pricing model:     For the three months ended  March 31,  2018 2017   Risk free interest rate 2.57% 1.91%  Dividend yield 0.7% 0.0%  Expected volatility 22% 20%  Expected lives 4.6 years 4.6 years  The following table summarizes the Company’s activities with respect to its stock option plans for the three months ended March 31, 2018 as follows (dolla rs and shares in thousands, except for per share data):     Weighted-  Weighted- Average  Average Remaining  Number Exercise Price Contractual Aggregate  of Shares Per Share Life (in years) Intrinsic Value  Outstanding at December 31, 2017 4,842 $ 100.12  Granted 922 $ 156.52  Exercised (180) $ 72.61  Canceled (8) $ 109.13  Outstanding at March 31, 2018 5,576 $ 110.32 4.6 $ 337,860  Exercisable at March 31, 2018 2,883 $ 95.84 3.5 $ 216,484  Unvested at March 31, 2018 2,693 $ 125.84 5.9 $ 121,376  The weighted-average per share fair value of options granted during the three months ended March 31, 2018 was $32.98 . The total intrinsic value for options exercised during the three months ended March 31, 2018 was $16.6 million. Restricted Stock Units The following table summarizes the Company’s restricted stock unit activity for the three months ended March 31, 2018 :     Weighted-  Average  Grant Date  Number of Fair Value per  Shares Share  (in thousands)  Outstanding at December 31, 2017 328 $ 110.20  Granted 128 $ 156.52  Vested (122) $ 110.61  Forfeited/canceled (3) $ 128.65  Outstanding at March 31, 2018 331 $ 127.83

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Taxes [Abstract]
Income Taxes	13. INC OME TAXES The primary reason for the difference in the Company’s effective tax rate and the U.S. statutory rate is a result of the Company’s REIT election and the Company having a full valuation allowance on the U.S. net deferred tax assets of the taxable REIT subsidiaries (“TRSs”). The Company has concluded that it is not more likely than not that its deferred tax assets will be realized and has recorded a full valuation allowance. A foreign tax provision is recognized because certain international subsidiaries of the Company have profitable operations or are in a net deferred tax liability position. The Company elected to be taxed as a REIT commencing with its taxable year ended December 31, 2016. As a REIT, the Company generally will be entitled to a deduction for dividends that it pays , and therefore , not subject to U.S. federal corporate income tax on that portion of its net income that it distributes to its shareholders. As a REIT, the Company will continue to pay U.S. federal income tax on earnings, if any, from assets and operations held through its TRSs. These assets and operations currently consist primarily of the Company’s site development services and its international operations. The Company’s international operations would continue to be subject, as applicable, to foreign taxes in the jurisdictions in which those operations are located. The Company may also be subject to a variety of taxes, including payroll taxes and state, local , and foreign income, property , and other taxes on its assets and operations. The Company’s determination as to the timing and amount of future dividend distributions will be based on a number of factors, including REIT distribution requirements, its existing federal net operating losses (“NOLs”) of approximately $1.0 billion as of December 31, 2017, the Company’s financial condition, earnings, debt covenants, and other possible uses of such funds. The Company may use these NOLs to offset its REIT taxable income, and thus any required distributions to shareholders may be reduced or eliminated until such time as the NOLs have been fully utilized. The Tax Cuts and Jobs Act (the “Tax Act”) was enacted on December 22, 2017. The Tax Act reduces the U . S . federal corporate income tax rate from 35% to 21% , requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax deferred and creates new taxes on certain foreign sourced earnings. The Company is applying the guidance in S taff Accounting Bulletin No. 118 when accounting for the enactment-date effects of the Tax Act. As of March 31, 2018 , the Company has not recognized any adjustments to the provisional amounts recorded at December 31, 2017. As additional guidance becomes available related to the Tax Act , the Company will continue to refine its calculations. These estimates may also be affected as the Company gains a more thorough understanding of the Tax Act. These changes may be material to income tax expense. The global intangible low-taxed income (“GILTI”) provisions of the Tax Act impose a tax on the income of certain foreign subsidiaries in excess of a specified return on tangible assets used by the foreign companies. FASB Staff Q&A, Topic 740, No. 5, Accounting for Global Intangible Low-Taxed Income, states that an entity can make an accounting policy election to either recognize deferred taxes for temporary basis differences expected to reverse as GILTI in future years or provide for the tax expense related to GILTI in the year the tax is incurred. Given the complexity of the GILTI provisions, the Company is still evaluating the effects of the GILTI provisions and has not yet determined the new accounting policy it intends to elect . At March 31, 2018 , because the Company is still evaluating the GILTI provisions and the analysis of future taxable income subject to GILTI, the Company has included GILTI related to current-year operations only and have not provided additional GILTI on deferred items.

Segment Data

Segment Data	3 Months Ended
	Mar. 31, 2018
Segment Data [Abstract]
Segment Data	14. SEGMENT DATA The Company operates principally in two business segments: site leasing and site development. The Company’s site leasing business includes two reportable segments, domestic site leasing and international site leasing. The Company’s business segments are strategic business units that offer different services. They are managed separately based on the fundamental differences in their operations. The site leasing segment includes results of the managed and sublease businesses. The site development segment includes the results of both consulting and construction related activities. The Company’s Chief Operating Decision Maker utilizes segment operating profit and operating income as his two measures of segment profit in assessing performance and allocating resources at the reportable segment level. The Company has applied the aggregation criteria to operations within the international site leasing segment on a basis that is consistent with management’s review of information and performance evaluations of the individual markets in this region . Revenues, cost of revenues (exclusive of depreciation, accretion and amortization), capital expenditures (including assets acquired through the issuance of shares of the Company’s Class A common stock) and identifiable assets pertaining to the segments in which the Company continues to operate are presented below.     Domestic Site Int'l Site Site Not Identified  Leasing Leasing Development by Segment Total   For the three months ended March 31, 2018 (in thousands)  Revenues $ 341,707 $ 88,835 $ 27,760 $ — $ 458,302  Cost of revenues (2) 65,015 27,802 22,520 — 115,337  Operating profit 276,692 61,033 5,240 — 342,965  Selling, general, and administrative 19,339 6,614 4,077 6,019 36,049  Acquisition related adjustments and expenses 1,786 1,258 — — 3,044  Asset impairment and decommission costs 6,726 1,502 278 — 8,506  Depreciation, amortization and accretion 123,458 39,680 642 1,618 165,398  Operating income (loss) 125,383 11,979 243 (7,637) 129,968  Other expense (principally interest expense  and other income (expense)) (89,841) (89,841)  Income before provision for income taxes 40,127  Cash capital expenditures (3) 71,019 77,056 267 636 148,978   For the three months ended March 31, 2017  Revenues $ 321,130 $ 76,420 $ 25,813 $ — $ 423,363  Cost of revenues (2) 65,427 23,955 21,588 — 110,970  Operating profit 255,703 52,465 4,225 — 312,393  Selling, general, and administrative 19,356 5,959 3,617 5,291 34,223  Acquisition related adjustments and expenses 1,901 1,068 — — 2,969  Asset impairment and decommission costs 7,430 816 105 — 8,351  Depreciation, amortization and accretion 123,896 32,825 711 1,599 159,031  Operating income (loss) 103,120 11,797 (208) (6,890) 107,819  Other expense (principally interest expense  and other income (expense)) (66,823) (66,823)  Income before provision for income taxes 40,996  Cash capital expenditures (3) 50,433 26,890 133 942 78,398           Domestic Site Int'l Site Site Not Identified  Leasing Leasing Development by Segment (1) Total   Assets (in thousands)  As of March 31, 2018 $ 5,139,407 $ 2,133,870 $ 53,144 $ 78,661 $ 7,405,082  As of December 31, 2017 $ 5,171,190 $ 2,028,479 $ 49,487 $ 71,049 $ 7,320,205  (1) Assets not identified by segment consist primarily of general corporate assets. (2) Excludes depreciation, amortization, and accretion. (3) Includes cash paid for capital expenditures and acquisitions and vehicle capital lease additions. Other than Brazil, no foreign country represented a material amount of total revenues in any of the periods presented. Site leasing revenue in Brazil was $61.2 million and $53.2 million for the three months ended March 31, 2018 and 2017 , respectively. Total long-lived assets in Brazil were $1,262.5 million and $1,278.9 million as of March 31, 2018 and December 31, 2017 , respectively.

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share	1 5 . EARNINGS PER SHARE Basic earnings per share was computed by dividing net income attributable to common shareholders by the weighted-average number of shares of Common Stock outstanding for each respective period. Diluted earnings per share was calculated by dividing net income attributable to common shareholders by the weighted-average number of shares of Common Stock outstanding adjusted for any dilutive Common Stock equivalents, including unvested restricted stock and shares issuable upon exercise of stock options as determined under the “If-Converted” method and also Common Stock warrants as determined under the “Treasury Stock” method. The following table sets forth basic and diluted net income per common share for the three months ended March 31, 2018 and 2017 (in thousands, except per share data):     For the three months  ended March 31,  2018 2017  Numerator:  Net income $ 31,545 $ 37,598  Denominator:  Basic weighted-average shares outstanding 116,494 121,049  Dilutive impact of stock options and restricted shares 1,799 685  Diluted weighted-average shares outstanding 118,293 121,734  Net income per common share:  Basic $ 0.27 $ 0.31  Diluted $ 0.27 $ 0.31  For the three months ended March 31, 2018 and 2017, the diluted weighted average number of common shares outstanding excluded an additional 0.3 million and 2.4 million shares, respectively, issuable upon exercise of the Company’s stock options because the impact would be anti-dilutive.

Basis of Presentation (Policy)

Basis of Presentation (Policy)	3 Months Ended
	Mar. 31, 2018
Basis of Presentation [Abstract]
Basis of Presentation	The accompanying consolidated financial statements should be read in conjunction with the Annual Report on Form 10-K for the fiscal year ended December 31, 2017 for SBA Communications Corporation and its subsidiaries (the “Company”). These financial statements have been prepared in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X and, therefore, omit or condense certain footnotes and other information normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States. In the opinion of the Company’s management, all adjustments (consisting of normal recurring accruals) considered necessary for fair financial statement presentation have been made. The results of operations for an interim period may not give a true indication of the results for the year. Certain reclassifications have been made to prior year amounts or balances to conform to the presentation adopted in the current year. The preparation of financial statements requires management to make estimates and assumptions that affect the amounts reported in consolidated financial statements and accompanying notes. While the Company believes that such estimates are fair when considered in conjunction with the consolidated financial statements and accompanying notes, the actual amounts, when known, may vary from these estimates.
Revenue Recognition and Accounts Receivable	Revenue Recognition and Accounts Receivable Revenue from site leasing is recognized on a straight-line basis over the current term of the related lease agreements, which are generally five to ten years. Receivables recorded related to the straight-lining of site leases are reflected in other assets on the Consolidated Balance Sheets. Rental amounts received in advance are recorded as deferred revenue on the Consolidated Balance Sheets. Revenues from site leasing represent 94% of the Company’s total revenues. Site development projects in which the Company performs consulting services include contracts on a fixed price basis . Site development projects are billed at contractual rates and revenue is recognized over time based on milestones achieved, which are determined based on costs incurred. Amounts billed in advance (collected or uncollected) are recorded as deferred revenue on the Consolidated Balance Sheets. Revenue from construction projects is recognized over time, determined by the percentage of cost incurred to date compared to management’s estimated total cost for each contract. This method is used because management considers total cost to be the best available measure of progress on the contracts. These amounts are based on estimates, and the uncertainty inherent in the estimates initially is reduced as work on the contracts nears completion. The asset “costs and estimated earnings in excess of billings on uncompleted contracts” represents costs incurred and revenues recognized in excess of amounts billed. The liability “billings in excess of costs and estimated earnings on uncompleted contracts,” included within other current liabilities on the Consolidated Balance Sheets, represents billings in excess of costs incurred and revenues recognized. Refer to Note 8 for further detail of costs and estimated earnings in excess of billings on uncompleted contracts. Provisions for estimated losses on uncompleted contracts are made in the period in which such losses are determined to be probable. The site development segment represents approximately 6% of the Company’s total revenues. The Company accounts for site development revenue in accordance with ASC 606, Revenue from Contracts with Customers, which the Company adopted on January 1, 2018 by applying the modified retrospective transition method. Payment terms do not result in any significant financing arrangements. Furthermore, these contracts do not typically include variable consideration; therefore, the transaction price that is recognized over time is generally the amount of the total contract. The cumulative effect of initially applying the new revenue standard had no impact on the Company’s financial results. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The adoption of the new standard will have no impact to net income on an ongoing basis. The accounts receivable balance was $101.1 million and $90.7 million as of March 31, 2018 and December 31, 2017 , respectively, of which $29.3 million and $20.8 million related to the site development segment as of March 31, 2018 and December 31, 2017 , respectively. The Company performs periodic credit evaluations of its customers. In addition, the Company monitors collections and payments from its customers and maintains a provision for estimated credit losses based upon historical experience, specific customer collection issues identified, and past due balances as determined based on contractual terms. Interest is charged on outstanding receivables from customers on a case by case basis in accordance with the terms of the respective contracts or agreements with those customers. Amounts determined to be uncollectible are written off against the allowance for doubtful accounts in the period in which uncollectibility is determined to be probable. Refer to Note 14 for further detail of the site development segment.
Foreign Currency Translation	Foreign Currency Translation All assets and liabilities of foreign subsidiaries that do not utilize the U.S. dollar as its functional currency are translated at period-end rates of exchange, while revenues and expenses are translated at monthly average rates of exchange prevailing during the period. Unrealized remeasurement gains and losses are reported as foreign currency translation adjustments through Accumulated Other Comprehensive Loss in the accompanying Consolidated Statement of Shareholders’ Deficit. For foreign subsidiaries where the U.S. dollar is the functional currency, monetary assets and liabilities of such subsidiaries, which are not denominated in U.S. dollars, are remeasured at exchange rates in effect at the balance sheet date, and revenues and expenses are remeasured at monthly average rates prevailing during the year. Unrealized translation gains and losses are reported as other income (expense), net in the Consolidated Statement of Operations.
Intercompany Loans Subject to Remeasurement	Intercompany Loans Subject to Remeasurement The Company has two wholly owned subsidiaries, Brazil Shareholder I, LLC, a Florida limited liability company, and SBA Torres Brasil, Limitada, a limitada existing under the laws of the Republic of Brazil, which have entered into intercompany loan agreements pursuant to which the entities may from time to time agree to lend/borrow amounts under the terms of each agreement. The first agreement entered into in November 2014 was for $750.0 million and was created to fund the acquisition of 1,641 towers in Brazil. The second agreement entered into in December 2017 was for $500.0 million and was created to fund the acquisition of 941 towers in Brazil. In accordance with Accounting Standards Codification (ASC) 830, the Company remeasures foreign denominated intercompany loans with the corresponding change in the balance being recorded in Other income (expense), net in the Consolidated Statement of Operations as settlement is anticipated or planned in the foreseeable future. For the three months ended March 31, 2018 and 2017 , the Company recorded a $1.6 million gain and a $13.7 million gain , respectively, on the remeasurement of intercompany loans due to changes in foreign exchange rates. As of March 31, 2018 , the aggregate amount outstanding under the two intercompany loan agreement s with the Company’s Brazilian subsidiary was $560.9 million.
Recent Accounting Pronouncements Not Yet Adopted	Recent Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU 2016-02, Leases. The standard requires lessees to recognize a right-of-use asset and a lease liability, initially measured at the present value of the lease payments for all leases with a term greater than 12 months. The accounting for lessors remains largely unchanged from existing guidance. This standard is effective for annual and interim periods beginning after December 15, 2018. Early adoption is permitted; however, the Company does not currently plan to early adopt. The Company has established a cross functional project plan and is assessing the impact of the standard on its consolidated financial statements. The Company expects this guidance to have a material impact on its consolidated balance sheet due to the recognition of right-of-use assets and lease liabilities for its ground leases. The Company does not expect adoption to have a significant impact on its lease classification or to have a material impact on its consolidated statement of operations.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Measurements [Abstract]
Summary Of Asset Impairment And Decommission Costs	   For the three months  ended March 31,  2018 2017   Asset impairment (1) $ 5,855 $ 3,014  Write-off of carrying value of decommissioned towers 2,001 3,971  Other third party decommission costs 650 1,366  Total asset impairment and decommission costs $ 8,506 $ 8,351 (1) Represents impairment charges resulting from the Company’s regular analysis of whether the future cash flows from certain towers are adequate to recover the carrying value of the investment in those towers.

Restricted Cash (Tables)

Restricted Cash (Tables)	3 Months Ended
	Mar. 31, 2018
Restricted Cash [Abstract]
Schedule of Cash, Cash Equivalents and Restricted Cash	   As of As of  March 31, 2018 December 31, 2017 Included on Balance Sheet   (in thousands)  Cash and cash equivalents $ 109,350 $ 68,783  Securitization escrow accounts 28,143 32,699 Restricted cash - current asset  Payment and performance bonds 229 225 Restricted cash - current asset  Surety bonds and workers compensation 2,596 2,588 Other assets - noncurrent  Cash held in escrow for acquisitions 24,502 — Other assets - noncurrent  Total cash, cash equivalents, and restricted cash $ 164,820 $ 104,295 

Prepaid Expenses and Other Cu27

Prepaid Expenses and Other Current Assets and Other Assets (Tables)	3 Months Ended
	Mar. 31, 2018
Prepaid Expenses and Other Current Assets and Other Assets [Abstract]
Schedule of Prepaid Expense and Other Current Assets	   As of As of  March 31, 2018 December 31, 2017   (in thousands)  Prepaid ground rent $ 31,257 $ 32,505  Other 19,659 17,211  Total prepaid expenses and other current assets $ 50,916 $ 49,716 
Schedule of Other Assets	   As of As of  March 31, 2018 December 31, 2017   (in thousands)  Prepaid ground rent $ 230,327 $ 220,493  Straight-line rent receivable 318,841 313,650  Deferred lease costs, net 27,519 27,703  Cash held in escrow for acquisitions 24,502 —  Other 96,995 88,349  Total other assets $ 698,184 $ 650,195 

Acquisitions (Tables)

Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2018
Acquisitions [Abstract]
Schedule of Acquisition Capital Expenditures	   For the three months  ended March 31,  2018 2017   (in thousands)  Acquisitions of towers and related intangible assets $ 108,355 $ 31,147  Land buyouts and other assets (1) 9,267 11,504  Total cash acquisition capital expenditures $ 117,622 $ 42,651  (1) In addition, the Company paid $6.6 million and $2.7 million for ground lease extensions and term easements on land underlying the Company’s towers during the three months ended March 31, 2018 and 2017 , respectively. The Company recorded these amounts in prepaid rent on its Consolidated Balance Sheets .

Intangible Assets, Net (Tables)

Intangible Assets, Net (Tables)	3 Months Ended
	Mar. 31, 2018
Intangible Assets, Net [Abstract]
Gross and Net Carrying Amounts for each Major Class of Intangible Assets	   As of March 31, 2018 As of December 31, 2017  Gross carrying Accumulated Net book Gross carrying Accumulated Net book  amount amortization value amount amortization value   (in thousands)  Current contract intangibles $ 4,425,965 $ (1,746,160) $ 2,679,805 $ 4,355,171 $ (1,673,270) $ 2,681,901  Network location intangibles 1,649,246 (728,411) 920,835 1,617,441 (701,211) 916,230  Intangible assets, net $ 6,075,211 $ (2,474,571) $ 3,600,640 $ 5,972,612 $ (2,374,481) $ 3,598,131 

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	3 Months Ended
	Mar. 31, 2018
Property and Equipment, Net [Abstract]
Property and Equipment, Net (Including Assets Held Under Capital Leases)	   As of As of  March 31, 2018 December 31, 2017   (in thousands)  Towers and related components $ 4,817,195 $ 4,772,807  Construction-in-process 35,175 34,689  Furniture, equipment, and vehicles 53,485 53,260  Land, buildings, and improvements 638,609 630,370  Total property and equipment 5,544,464 5,491,126  Less: accumulated depreciation (2,740,986) (2,678,780)  Property and equipment, net $ 2,803,478 $ 2,812,346 

Costs and Estimated Earnings 31

Costs and Estimated Earnings on Uncompleted Contracts (Tables)	3 Months Ended
	Mar. 31, 2018
Costs and Estimated Earnings on Uncompleted Contracts [Abstract]
Summary of Costs and Estimated Earnings on Uncompleted Contracts	   As of As of  March 31, 2018 December 31, 2017   (in thousands)  Costs incurred on uncompleted contracts $ 33,232 $ 31,404  Estimated earnings 11,836 10,541  Billings to date (32,495) (24,771)  $ 12,573 $ 17,174 
Costs and Estimated Earnings on Uncompleted Contracts Accompanying Consolidated Balance Sheets	   As of As of  March 31, 2018 December 31, 2017   (in thousands)  Costs and estimated earnings in excess of billings on uncompleted contracts $ 13,039 $ 17,437  Billings in excess of costs and estimated earnings on  uncompleted contracts (included in Other current liabilities) (466) (263)  $ 12,573 $ 17,174 

Accrued Expenses (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2018
Accrued Expenses [Abstract]
Schedule of Accrued Expenses	   As of As of  March 31, 2018 December 31, 2017   (in thousands)  Accrued earnouts on business combinations $ 2,503 $ 2,470  Salaries and benefits 5,755 13,506  Real estate and property taxes 6,900 7,125  Non-cash capital expenditures 10,352 12,408  Other 34,713 34,353  Total accrued expenses $ 60,223 $ 69,862 

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Debt [Abstract]
Schedule of Carrying and Principal Values of Debt	   As of As of  March 31, 2018 December 31, 2017  Maturity Date Principal Balance Fair Value Carrying Value Principal Balance Fair Value Carrying Value  2014 Senior Notes Jul. 15, 2022 $ 750,000 $ 753,750 $ 739,617 $ 750,000 $ 770,625 $ 739,079  2016 Senior Notes Sep. 1, 2024 1,100,000 1,075,250 1,081,857 1,100,000 1,127,500 1,081,262  2017 Senior Notes Oct. 1, 2022 750,000 718,125 741,846 750,000 750,938 741,437  2013-1C Tower Securities Apr. 10, 2018 — — — 425,000 423,853 424,482  2013-2C Tower Securities Apr. 11, 2023 575,000 568,071 568,881 575,000 578,433 568,609  2013-1D Tower Securities Ap. 10, 2018 — — — 330,000 330,145 329,585  2014-1C Tower Securities Oct. 8, 2019 920,000 910,395 915,621 920,000 915,216 914,929  2014-2C Tower Securities Oct. 8, 2024 620,000 607,067 613,672 620,000 620,942 613,461  2015-1C Tower Securities Oct. 8, 2020 500,000 492,260 494,028 500,000 496,840 493,474  2016-1C Tower Securities Jul. 9, 2021 700,000 691,726 693,578 700,000 691,166 693,118  2017-1C Tower Securities Apr. 11, 2022 760,000 740,992 751,548 760,000 751,404 751,076  2018-1C Tower Securities Mar. 9, 2023 640,000 638,650 631,939 — — —  Revolving Credit Facility Feb. 5, 2020 235,000 235,000 235,000 40,000 40,000 40,000  2014 Term Loan Mar. 24, 2021 1,443,750 1,447,359 1,436,207 1,447,500 1,451,119 1,439,373  2015 Term Loan Jun. 10, 2022 486,250 486,250 479,892 487,500 488,109 480,801  Total debt $ 9,480,000 $ 9,364,895 $ 9,383,686 $ 9,405,000 $ 9,436,290 $ 9,310,686  Less: current maturities of long-term debt (20,000) (20,000)  Total long-term debt, net of current maturities $ 9,363,686 $ 9,290,686 
Schedule of Cash and Non-Cash Interest Expense	   For the three months ended March 31,  2018 2017  Cash Non-cash Cash Non-cash  Interest Interest Interest Interest   (in thousands)  2014 Senior Notes $ 9,141 $ 187 $ 9,141 $ 178  2016 Senior Notes 13,406 246 13,406 234  2017 Senior Notes 7,500 — — —  2012 Tower Securities — — 4,524 —  2013 Tower Securities 9,475 — 10,804 —  2014 Tower Securities 12,785 — 12,785 —  2015-1C Tower Securities 3,985 — 3,985 —  2016-1C Tower Securities 5,090 — 5,090 —  2017-1C Tower Securities 6,085 — — —  2018-1C Tower Securities 1,362 — — —  Revolving Credit Facility 1,601 — 2,770 —  2014 Term Loan 13,947 131 11,284 128  2015 Term Loan 4,697 169 3,800 165  Other (151) — 13 —  Total $ 88,923 $ 733 $ 77,602 $ 705 

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2018
Stock-Based Compensation [Abstract]
Schedule of Assumptions Used to Estimate Fair Value of Stock Options	   For the three months ended  March 31,  2018 2017   Risk free interest rate 2.57% 1.91%  Dividend yield 0.7% 0.0%  Expected volatility 22% 20%  Expected lives 4.6 years 4.6 years 
Summary of Stock Option Activity	   Weighted-  Weighted- Average  Average Remaining  Number Exercise Price Contractual Aggregate  of Shares Per Share Life (in years) Intrinsic Value  Outstanding at December 31, 2017 4,842 $ 100.12  Granted 922 $ 156.52  Exercised (180) $ 72.61  Canceled (8) $ 109.13  Outstanding at March 31, 2018 5,576 $ 110.32 4.6 $ 337,860  Exercisable at March 31, 2018 2,883 $ 95.84 3.5 $ 216,484  Unvested at March 31, 2018 2,693 $ 125.84 5.9 $ 121,376 
Summary of Restricted Stock Unit Activity	   Weighted-  Average  Grant Date  Number of Fair Value per  Shares Share  (in thousands)  Outstanding at December 31, 2017 328 $ 110.20  Granted 128 $ 156.52  Vested (122) $ 110.61  Forfeited/canceled (3) $ 128.65  Outstanding at March 31, 2018 331 $ 127.83 

Segment Data (Tables)

Segment Data (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Data [Abstract]
Segment Reporting Information Disclosure	   Domestic Site Int'l Site Site Not Identified  Leasing Leasing Development by Segment Total   For the three months ended March 31, 2018 (in thousands)  Revenues $ 341,707 $ 88,835 $ 27,760 $ — $ 458,302  Cost of revenues (2) 65,015 27,802 22,520 — 115,337  Operating profit 276,692 61,033 5,240 — 342,965  Selling, general, and administrative 19,339 6,614 4,077 6,019 36,049  Acquisition related adjustments and expenses 1,786 1,258 — — 3,044  Asset impairment and decommission costs 6,726 1,502 278 — 8,506  Depreciation, amortization and accretion 123,458 39,680 642 1,618 165,398  Operating income (loss) 125,383 11,979 243 (7,637) 129,968  Other expense (principally interest expense  and other income (expense)) (89,841) (89,841)  Income before provision for income taxes 40,127  Cash capital expenditures (3) 71,019 77,056 267 636 148,978   For the three months ended March 31, 2017  Revenues $ 321,130 $ 76,420 $ 25,813 $ — $ 423,363  Cost of revenues (2) 65,427 23,955 21,588 — 110,970  Operating profit 255,703 52,465 4,225 — 312,393  Selling, general, and administrative 19,356 5,959 3,617 5,291 34,223  Acquisition related adjustments and expenses 1,901 1,068 — — 2,969  Asset impairment and decommission costs 7,430 816 105 — 8,351  Depreciation, amortization and accretion 123,896 32,825 711 1,599 159,031  Operating income (loss) 103,120 11,797 (208) (6,890) 107,819  Other expense (principally interest expense  and other income (expense)) (66,823) (66,823)  Income before provision for income taxes 40,996  Cash capital expenditures (3) 50,433 26,890 133 942 78,398           Domestic Site Int'l Site Site Not Identified  Leasing Leasing Development by Segment (1) Total   Assets (in thousands)  As of March 31, 2018 $ 5,139,407 $ 2,133,870 $ 53,144 $ 78,661 $ 7,405,082  As of December 31, 2017 $ 5,171,190 $ 2,028,479 $ 49,487 $ 71,049 $ 7,320,205  (1) Assets not identified by segment consist primarily of general corporate assets. (2) Excludes depreciation, amortization, and accretion. (3) Includes cash paid for capital expenditures and acquisitions and vehicle capital lease additions.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Weighted-Average Shares of Common Stock Outstanding used in Calculation of Basic and Diluted Earnings Per Share	   For the three months  ended March 31,  2018 2017  Numerator:  Net income $ 31,545 $ 37,598  Denominator:  Basic weighted-average shares outstanding 116,494 121,049  Dilutive impact of stock options and restricted shares 1,799 685  Diluted weighted-average shares outstanding 118,293 121,734  Net income per common share:  Basic $ 0.27 $ 0.31  Diluted $ 0.27 $ 0.31 

Basis of Presentation (Narrativ

Basis of Presentation (Narrative) (Details) $ in Thousands	1 Months Ended			3 Months Ended
	Apr. 30, 2018item	Dec. 31, 2017USD ($)item	Nov. 30, 2014USD ($)item	Mar. 31, 2018USD ($)entity	Mar. 31, 2017USD ($)
Basis Of Presentation [Line Items]
Accounts receivable, net		$ 90,673		$ 101,103
Number of wholly owned subsidiaries that entered into intercompany loan agreement | entity				2
Intercompany loan maximum lend/borrow amount		$ 500,000	$ 750,000
Number of towers acquired | item		941	1,641
Gain (loss) on remeasurement of U.S. dollar denominated intercompany loan				$ 1,623	$ 13,659
Intercompany foreign currency outstanding balance				560,900
Subsequent Event [Member]
Basis Of Presentation [Line Items]
Number of towers acquired | item	190
Site Development [Member]
Basis Of Presentation [Line Items]
Accounts receivable, net		$ 20,800		$ 29,300
Site Development [Member] | Revenue [Member]
Basis Of Presentation [Line Items]
Concentration risk percentage of revenue				6.00%
Minimum [Member]
Basis Of Presentation [Line Items]
Lease term				5 years
Maximum [Member]
Basis Of Presentation [Line Items]
Lease term				10 years

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	May 07, 2018	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accrued earnouts		$ 2.5	$ 2.5
Performance targets, maximum potential obligation		15.5	11.1
Treasury securities		0.2	0.2
Held-to-maturity investments, carrying value		0.5	0.5
Held-to-maturity investments, fair value		0.5	0.5
Business Combinations and Asset Acquisitions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Performance targets, maximum potential obligation		$ 3.1	$ 3.1
Revolving Credit Facility [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Basis spread on variable interest rate		1.375%
Revolving Credit Facility [Member] | Minimum [Member] | Subsequent Event [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Basis spread on variable interest rate	1.125%
Revolving Credit Facility [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Basis spread on variable interest rate		2.00%
Revolving Credit Facility [Member] | Maximum [Member] | Subsequent Event [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Basis spread on variable interest rate	1.75%

Fair Value Measurements (Summar

Fair Value Measurements (Summary of Asset Impairment and Decommission Costs) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Asset impairment	$ 5,855	$ 3,014
Other third party decommission costs	650	1,366
Total asset impairment and decommission costs	8,506	8,351
Decommissioned Towers [Member]
Write-offs relating to long-lived assets and intangibles	$ 2,001	$ 3,971

Restricted Cash (Narrative) (De

Restricted Cash (Narrative) (Details)	1 Months Ended
	Apr. 30, 2018USD ($)item	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Restricted Cash And Cash Equivalents Items [Line Items]
Surety, payment and performance bonds		$ 39,600,000	$ 39,500,000
Collateral payment for performance bonds		0	0
Collateral related to workers compensation policy		2,500,000	$ 2,500,000
Subsequent Event [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Number of acquisitions closed | item	1
Escrow disbursement for acquisition	$ 10,000,000
Cash Held in Escrow for Acquisitions [Member] | Other Assets - Noncurrent [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash - noncurrent asset		$ 24,502,000

Restricted Cash (Schedule of Ca

Restricted Cash (Schedule of Cash, Cash Equivalents and Restricted Cash) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Restricted Cash And Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 109,350	$ 68,783
Restricted cash - current asset	28,372	32,924
Total cash, cash equivalents, and restricted cash	164,820	104,295	$ 165,471	$ 185,970
Securitization Escrow Accounts [Member] | Restricted Cash - Current Asset [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash - current asset	28,143	32,699
Payment and Performance Bonds [Member] | Restricted Cash - Current Asset [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash - current asset	229	225
Surety Bonds and Workers Compensation [Member] | Other Assets - Noncurrent [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash - noncurrent asset	2,596	$ 2,588
Cash Held in Escrow for Acquisitions [Member] | Other Assets - Noncurrent [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash - noncurrent asset	$ 24,502

Prepaid Expenses and Other Cu42

Prepaid Expenses and Other Current Assets and Other Assets (Schedule of Prepaid Expense and Other Current Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Prepaid Expenses and Other Current Assets and Other Assets [Abstract]
Prepaid ground rent	$ 31,257	$ 32,505
Other	19,659	17,211
Total prepaid expenses and other current assets	$ 50,916	$ 49,716

Prepaid Expenses and Other Cu43

Prepaid Expenses and Other Current Assets and Other Assets (Schedule Of Other Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Prepaid Expenses and Other Current Assets and Other Assets [Abstract]
Prepaid ground rent	$ 230,327	$ 220,493
Straight-line rent receivable	318,841	313,650
Deferred lease costs, net	27,519	27,703
Cash held in escrow for acquisitions	24,502
Other	96,995	88,349
Total other assets	$ 698,184	$ 650,195

Acquisitions (Narrative) (Detai

Acquisitions (Narrative) (Details) $ in Millions	1 Months Ended			3 Months Ended
	Apr. 30, 2018USD ($)item	Dec. 31, 2017item	Nov. 30, 2014item	Mar. 31, 2018USD ($)item
Business Acquisition [Line Items]
Number of towers acquired | item		941	1,641
Other Acquisitions [Member]
Business Acquisition [Line Items]
Number of towers acquired | item				334
Property and equipment				$ 23.2
Intangible assets				101.3
Working capital adjustments				$ 16.2
Subsequent Event [Member]
Business Acquisition [Line Items]
Number of towers acquired | item	190
Cash paid for acquisition	$ 119.5

Acquisitions (Schedule Of Acqui

Acquisitions (Schedule Of Acquisition Capital Expenditures) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Acquisitions [Abstract]
Acquisitions of towers and related intangible assets	$ 108,355	$ 31,147
Land buyouts and other assets	9,267	11,504
Total cash acquisition capital expenditures	117,622	42,651
Ground lease extensions	$ 6,600	$ 2,700

Intangible Assets, Net (Narrati

Intangible Assets, Net (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Intangible Assets, Net [Abstract]
Intangible assets, useful life	15 years
Amortization expense	$ 100.3	$ 94.9

Intangible Assets, Net (Gross a

Intangible Assets, Net (Gross and Net Carrying Amounts for each Major Class of Intangible Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 6,075,211	$ 5,972,612
Accumulated amortization	(2,474,571)	(2,374,481)
Net book value	3,600,640	3,598,131
Current Contract Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	4,425,965	4,355,171
Accumulated amortization	(1,746,160)	(1,673,270)
Net book value	2,679,805	2,681,901
Network Location Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	1,649,246	1,617,441
Accumulated amortization	(728,411)	(701,211)
Net book value	$ 920,835	$ 916,230

Property and Equipment, Net (Na

Property and Equipment, Net (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Property and Equipment, Net [Abstract]
Depreciation expense	$ 65	$ 64.1
Non-cash capital expenditures	$ 10.4		$ 12.4

Property and Equipment, Net (Pr

Property and Equipment, Net (Property and Equipment, Net (Including Assets Held Under Capital Leases)) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 5,544,464	$ 5,491,126
Less: accumulated depreciation	(2,740,986)	(2,678,780)
Property and equipment, net	2,803,478	2,812,346
Towers and Related Components [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	4,817,195	4,772,807
Construction-In-Process [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	35,175	34,689
Furniture, equipment and vehicles [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	53,485	53,260
Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 638,609	$ 630,370

Costs and Estimated Earnings 50

Costs and Estimated Earnings on Uncompleted Contracts (Narrative) (Details) - customer	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Costs and Estimated Earnings on Uncompleted Contracts [Abstract]
Costs and estimated earnings in excess of billings on uncompleted contracts, net of billings in excess of costs and estimated earnings, percentage comprised by significant customers	87.40%	87.90%
Number of significant customers	8	8

Costs and Estimated Earnings 51

Costs and Estimated Earnings on Uncompleted Contracts (Summary of Costs and Estimated Earnings on Uncompleted Contracts) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Costs and Estimated Earnings on Uncompleted Contracts [Abstract]
Costs incurred on uncompleted contracts	$ 33,232	$ 31,404
Estimated earnings	11,836	10,541
Billings to date	(32,495)	(24,771)
Costs and estimated earnings on uncompleted contracts	$ 12,573	$ 17,174

Costs and Estimated Earnings 52

Costs and Estimated Earnings on Uncompleted Contracts (Costs and Estimated Earnings on Uncompleted Contracts Accompanying Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Costs and Estimated Earnings on Uncompleted Contracts [Abstract]
Costs and estimated earnings in excess of billings on uncompleted contracts	$ 13,039	$ 17,437
Billings in excess of costs and estimated earnings on uncompleted contracts (included in Other current liabilities)	(466)	(263)
Costs and estimated earnings on uncompleted contracts	$ 12,573	$ 17,174

Accrued Expenses (Schedule of A

Accrued Expenses (Schedule of Accrued Expenses) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accrued Expenses [Abstract]
Accrued earnouts on business combinations	$ 2,503	$ 2,470
Salaries and benefits	5,755	13,506
Real estate and property taxes	6,900	7,125
Non-cash capital expenditures	10,352	12,408
Other	34,713	34,353
Total accrued expenses	$ 60,223	$ 69,862

Debt (Senior Credit Agreement)

Debt (Senior Credit Agreement) (Narrative) (Details) - USD ($)	May 07, 2018	Apr. 11, 2018	Oct. 13, 2017	Apr. 30, 2018	Mar. 31, 2018	Mar. 31, 2017
Line of Credit Facility [Line Items]
Repayments of revolving credit facility					$ 70,000,000	$ 110,000,000
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity					$ 1,000,000,000
Revolving credit facility, effective interest rate					3.74%
Line of credit facility, commitment fee					0.25%
Borrowings on the revolving credit facility					$ 265,000,000
Repayments of revolving credit facility			$ 460,000,000
Revolving Credit Facility [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Borrowings on the revolving credit facility				$ 200,000,000
Repayments of revolving credit facility				$ 335,000,000
Line of credit facility, outstanding	$ 100,000,000
Amended Revolving Credit Facility [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		$ 1,250,000,000
Revolving credit facility, maturity date		Apr. 11, 2023
Revolving credit facility, effective interest rate	3.26%
Minimum [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate					1.375%
Minimum [Member] | Revolving Credit Facility [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	1.125%
Minimum [Member] | Revolving Credit Facility [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate					0.375%
Minimum [Member] | Amended Revolving Credit Facility [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Line of credit facility, commitment fee		0.20%
Minimum [Member] | Amended Revolving Credit Facility [Member] | Eurodollar [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate		1.125%
Minimum [Member] | Amended Revolving Credit Facility [Member] | Base Rate [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate		0.125%
Maximum [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate					2.00%
Maximum [Member] | Revolving Credit Facility [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	1.75%
Maximum [Member] | Revolving Credit Facility [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate					1.00%
Maximum [Member] | Amended Revolving Credit Facility [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Line of credit facility, commitment fee		0.25%
Maximum [Member] | Amended Revolving Credit Facility [Member] | Eurodollar [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate		1.75%
Maximum [Member] | Amended Revolving Credit Facility [Member] | Base Rate [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate		0.75%
2018 Term Loan B [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt instrument, face amount		$ 2,400,000,000
2018 Term Loan B [Member] | Eurodollar [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate		2.00%
2018 Term Loan B [Member] | Base Rate [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate		1.00%

Debt (Term Loans under the Seni

Debt (Term Loans under the Senior Credit Agreement) (Narrative) (Details) - USD ($)	Apr. 11, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Debt Instrument [Line Items]
Debt instrument, principal balance		$ 9,480,000,000		$ 9,405,000,000
Repayment of term loans		5,000,000	$ 5,000,000
2014 Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 1,500,000,000
Debt instrument, maturity date		Mar. 24, 2021
Term Loan, percentage of par value		99.75%
Coupon rate of notes		3.99%
Quarterly payments		$ 3,800,000
Debt instrument, principal balance		1,443,750,000		1,447,500,000
Repayment of term loans		3,800,000
Deferred financing fees		14,100,000
2015 Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 500,000,000
Debt instrument, maturity date		Jun. 10, 2022
Term Loan, percentage of par value		99.00%
Coupon rate of notes		3.99%
Quarterly payments		$ 1,300,000
Debt instrument, principal balance		486,250,000		$ 487,500,000
Repayment of term loans		1,300,000
Deferred financing fees		5,500,000
2014 and 2015 Term Loans [Member]
Debt Instrument [Line Items]
Debt instrument, principal balance		$ 1,930,000,000
Base Rate [Member] | 2014 Term Loan [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate		1.25%
Base rate floor		0.00%
Base Rate [Member] | 2015 Term Loan [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate		1.25%
Base rate floor		0.00%
Eurodollar [Member] | 2014 Term Loan [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate		2.25%
Eurodollar rate floor		0.00%
Eurodollar [Member] | 2015 Term Loan [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate		2.25%
Eurodollar rate floor		0.00%
Subsequent Event [Member] | 2014 Term Loan [Member]
Debt Instrument [Line Items]
Repayment of term loans	$ 1,443,800,000
Deferred financing fees	5,800,000
Discount related to debt	1,700,000
Subsequent Event [Member] | 2015 Term Loan [Member]
Debt Instrument [Line Items]
Repayment of term loans	486,300,000
Deferred financing fees	3,200,000
Discount related to debt	3,100,000
Subsequent Event [Member] | 2018 Term Loan B [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 2,400,000,000
Debt instrument, maturity date	Apr. 11, 2025
Percentage of par value price for issuance of term loan	99.75%
Quarterly payments	$ 6,000,000
Deferred financing fees	$ 15,900,000
Subsequent Event [Member] | Base Rate [Member] | 2018 Term Loan B [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate	1.00%
Base rate floor	0.00%
Subsequent Event [Member] | Eurodollar [Member] | 2018 Term Loan B [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate	2.00%
Eurodollar rate floor	0.00%

Debt (Secured Tower Revenue Sec

Debt (Secured Tower Revenue Securities) (Narrative) (Details) - USD ($)	Mar. 09, 2018	Apr. 17, 2017	Jul. 07, 2016	Oct. 14, 2015	Oct. 15, 2014	Apr. 18, 2013	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt							$ 9,383,686,000	$ 9,310,686,000
2010-2C Tower Securities [Member]
Debt Instrument [Line Items]
Repayments of long-term debt			$ 550,000,000
2012-1C Tower Securities [Member]
Debt Instrument [Line Items]
Repayments of long-term debt		$ 610,000,000
2013 Tower Securities [Member]
Debt Instrument [Line Items]
Deferred financing fees						$ 25,500,000
Debt instrument, weighted average interest rate						3.218%
Long-term debt						$ 1,330,000,000
2013-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount						$ 425,000,000
Debt instrument, interest rate, stated percentage						2.24%
Repayment date of debt instrument						Apr. 10, 2018
Debt instrument, maturity date						Apr. 9, 2043	Apr. 10, 2018
Repayments of long-term debt	$ 425,000,000
Long-term debt								424,482,000
2013-2C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount						$ 575,000,000
Debt instrument, interest rate, stated percentage						3.722%
Repayment date of debt instrument						Apr. 11, 2023
Debt instrument, maturity date						Apr. 9, 2048	Apr. 11, 2023
Long-term debt							$ 568,881,000	568,609,000
2013-1D Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount						$ 330,000,000
Debt instrument, interest rate, stated percentage						3.598%
Repayment date of debt instrument						Apr. 10, 2018
Debt instrument, maturity date						Apr. 9, 2043	Apr. 10, 2018
Repayments of long-term debt	330,000,000
Long-term debt								329,585,000
2014 Tower Securities [Member]
Debt Instrument [Line Items]
Deferred financing fees					$ 22,500,000
Debt instrument, weighted average interest rate					3.289%
Long-term debt					$ 1,540,000,000
2014-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount					$ 920,000,000
Debt instrument, interest rate, stated percentage					2.898%
Repayment date of debt instrument					Oct. 8, 2019
Debt instrument, maturity date					Oct. 11, 2044		Oct. 8, 2019
Long-term debt							$ 915,621,000	914,929,000
2014-2C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount					$ 620,000,000
Debt instrument, interest rate, stated percentage					3.869%
Repayment date of debt instrument					Oct. 8, 2024
Debt instrument, maturity date					Oct. 8, 2049		Oct. 8, 2024
Long-term debt							$ 613,672,000	613,461,000
2015-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 500,000,000
Debt instrument, interest rate, stated percentage				3.156%
Repayment date of debt instrument				Oct. 8, 2020
Debt instrument, maturity date				Oct. 10, 2045			Oct. 8, 2020
Deferred financing fees				$ 11,200,000
Long-term debt							$ 494,028,000	493,474,000
2016-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 700,000,000
Debt instrument, interest rate, stated percentage			2.877%
Repayment date of debt instrument			Jul. 9, 2021
Debt instrument, maturity date			Jul. 10, 2046				Jul. 9, 2021
Deferred financing fees			$ 9,500,000
Long-term debt							$ 693,578,000	693,118,000
2017-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 760,000,000
Debt instrument, interest rate, stated percentage		3.168%
Repayment date of debt instrument		Apr. 11, 2022
Debt instrument, maturity date		Apr. 9, 2047					Apr. 11, 2022
Deferred financing fees		$ 10,200,000
Long-term debt							$ 751,548,000	$ 751,076,000
2017-1R Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 40,000,000
Debt instrument, interest rate, stated percentage		4.459%
Repayment date of debt instrument		Apr. 11, 2022
Debt instrument, maturity date		Apr. 9, 2047
2018-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 640,000,000
Debt instrument, interest rate, stated percentage	3.448%
Repayment date of debt instrument	Mar. 9, 2023
Debt instrument, maturity date	Mar. 9, 2048
Long-term debt							$ 631,939,000
2013 1-C and 2013 1-D Tower Securities [Member]
Debt Instrument [Line Items]
Deferred financing fees	$ 8,200,000
2018-1R Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 33,700,000
Debt instrument, interest rate, stated percentage	4.949%
Repayment date of debt instrument	Mar. 9, 2023
Debt instrument, maturity date	Mar. 9, 2048
Mortgage Loan [Member]
Debt Instrument [Line Items]
Debt instrument, increase	$ 673,700,000
Debt instrument, decrease after giving effect to prepayment of loan components	$ 81,300,000

Debt (Senior Notes) (Narrative)

Debt (Senior Notes) (Narrative) (Details) - USD ($) $ in Thousands	Oct. 13, 2017	Aug. 15, 2016	Jul. 01, 2014	Apr. 30, 2018	Mar. 31, 2018	Mar. 31, 2017
Debt Instrument [Line Items]
Repayments of revolving credit facility					$ 70,000	$ 110,000
5.75% Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage		5.75%
Repayments of unsecured debt		$ 800,000
5.625% Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage		5.625%
Repayments of unsecured debt		$ 250,000
2014 Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes			$ 750,000
Debt instrument, maturity date					Jul. 15, 2022
Debt instrument, interest rate, stated percentage			4.875%
Percentage of face value price for issuance of senior notes			99.178%
Interest payable dates					January 15 and July 15
Deferred financing fees			$ 11,600
2014 Senior Notes [Member] | Redemption, Period One [Member]
Debt Instrument [Line Items]
Redemption price, percentage					103.656%
2014 Senior Notes [Member] | Redemption, Period Two [Member]
Debt Instrument [Line Items]
Redemption price, percentage					102.438%
2014 Senior Notes [Member] | Redemption, Period Three [Member]
Debt Instrument [Line Items]
Redemption price, percentage					101.219%
2014 Senior Notes [Member] | Redemption, Period Four [Member]
Debt Instrument [Line Items]
Redemption price, percentage					100.00%
2016 Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes		$ 1,100,000
Debt instrument, maturity date					Sep. 1, 2024
Debt instrument, interest rate, stated percentage		4.875%
Percentage of face value price for issuance of senior notes		99.178%
Interest payable dates					March 1 and September 1
Deferred financing fees		$ 12,800
Redemption price, percentage					104.875%
2016 Senior Notes [Member] | Redemption, Period One [Member]
Debt Instrument [Line Items]
Redemption price, percentage					103.656%
2016 Senior Notes [Member] | Redemption, Period Two [Member]
Debt Instrument [Line Items]
Redemption price, percentage					102.438%
2016 Senior Notes [Member] | Redemption, Period Three [Member]
Debt Instrument [Line Items]
Redemption price, percentage					101.219%
2016 Senior Notes [Member] | Redemption, Period Four [Member]
Debt Instrument [Line Items]
Redemption price, percentage					100.00%
2017 Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes	$ 750,000
Debt instrument, maturity date	Oct. 1, 2022
Debt instrument, interest rate, stated percentage	4.00%
Interest payable dates					April 1 and October 1
Deferred financing fees	$ 8,900
Redemption price, percentage					104.00%
Aggregate redemption price, percentage					35.00%
2017 Senior Notes [Member] | Redemption, Period One [Member]
Debt Instrument [Line Items]
Redemption price, percentage					102.00%
2017 Senior Notes [Member] | Redemption, Period Two [Member]
Debt Instrument [Line Items]
Redemption price, percentage					101.00%
2017 Senior Notes [Member] | Redemption, Period Three [Member]
Debt Instrument [Line Items]
Redemption price, percentage					100.00%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date					Feb. 5, 2020
Repayments of revolving credit facility	$ 460,000
Revolving Credit Facility [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Repayments of revolving credit facility				$ 335,000

Debt (Schedule of Carrying and

Debt (Schedule of Carrying and Principal Values of Debt) (Details) - USD ($)	Mar. 09, 2018	Oct. 13, 2017	Apr. 17, 2017	Jul. 07, 2016	Oct. 14, 2015	Oct. 15, 2014	Apr. 18, 2013	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Principal Balance								$ 9,480,000,000	$ 9,405,000,000
Fair Value								9,364,895,000	9,436,290,000
Carrying Value								9,383,686,000	9,310,686,000
Less: current maturities of long-term debt								(20,000,000)	(20,000,000)
Total long-term debt, net of current maturities								9,363,686,000	9,290,686,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal Balance								235,000,000	40,000,000
Fair Value								235,000,000	40,000,000
Carrying Value								$ 235,000,000	40,000,000
Debt instrument, maturity date								Feb. 5, 2020
2014 Senior Notes [Member]
Debt Instrument [Line Items]
Principal Balance								$ 750,000,000	750,000,000
Fair Value								753,750,000	770,625,000
Carrying Value								$ 739,617,000	739,079,000
Debt instrument, maturity date								Jul. 15, 2022
2016 Senior Notes [Member]
Debt Instrument [Line Items]
Principal Balance								$ 1,100,000,000	1,100,000,000
Fair Value								1,075,250,000	1,127,500,000
Carrying Value								$ 1,081,857,000	1,081,262,000
Debt instrument, maturity date								Sep. 1, 2024
2017 Senior Notes [Member]
Debt Instrument [Line Items]
Principal Balance								$ 750,000,000	750,000,000
Fair Value								718,125,000	750,938,000
Carrying Value								$ 741,846,000	741,437,000
Debt instrument, maturity date		Oct. 1, 2022
2013-1C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance									425,000,000
Fair Value									423,853,000
Carrying Value									424,482,000
Debt instrument, maturity date							Apr. 9, 2043	Apr. 10, 2018
2013-2C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 575,000,000	575,000,000
Fair Value								568,071,000	578,433,000
Carrying Value								$ 568,881,000	568,609,000
Debt instrument, maturity date							Apr. 9, 2048	Apr. 11, 2023
2013-1D Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance									330,000,000
Fair Value									330,145,000
Carrying Value									329,585,000
Debt instrument, maturity date							Apr. 9, 2043	Apr. 10, 2018
2014-1C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 920,000,000	920,000,000
Fair Value								910,395,000	915,216,000
Carrying Value								$ 915,621,000	914,929,000
Debt instrument, maturity date						Oct. 11, 2044		Oct. 8, 2019
2014-2C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 620,000,000	620,000,000
Fair Value								607,067,000	620,942,000
Carrying Value								$ 613,672,000	613,461,000
Debt instrument, maturity date						Oct. 8, 2049		Oct. 8, 2024
2015-1C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 500,000,000	500,000,000
Fair Value								492,260,000	496,840,000
Carrying Value								$ 494,028,000	493,474,000
Debt instrument, maturity date					Oct. 10, 2045			Oct. 8, 2020
2016-1C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 700,000,000	700,000,000
Fair Value								691,726,000	691,166,000
Carrying Value								$ 693,578,000	693,118,000
Debt instrument, maturity date				Jul. 10, 2046				Jul. 9, 2021
2017-1C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 760,000,000	760,000,000
Fair Value								740,992,000	751,404,000
Carrying Value								$ 751,548,000	751,076,000
Debt instrument, maturity date			Apr. 9, 2047					Apr. 11, 2022
2018-1C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 640,000,000
Fair Value								638,650,000
Carrying Value								631,939,000
Debt instrument, maturity date	Mar. 9, 2048
2014 Term Loan [Member]
Debt Instrument [Line Items]
Principal Balance								1,443,750,000	1,447,500,000
Fair Value								1,447,359,000	1,451,119,000
Carrying Value								$ 1,436,207,000	1,439,373,000
Debt instrument, maturity date								Mar. 24, 2021
2015 Term Loan [Member]
Debt Instrument [Line Items]
Principal Balance								$ 486,250,000	487,500,000
Fair Value								486,250,000	488,109,000
Carrying Value								$ 479,892,000	$ 480,801,000
Debt instrument, maturity date								Jun. 10, 2022

Debt (Schedule of Cash and Non-

Debt (Schedule of Cash and Non-Cash Interest Expense) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Debt Instrument [Line Items]
Cash Interest	$ 88,923	$ 77,602
Non-cash Interest	733	705
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Cash Interest	1,601	2,770
2014 Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest	9,141	9,141
Non-cash Interest	187	178
2016 Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest	13,406	13,406
Non-cash Interest	246	234
2017 Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest	7,500
2012 Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest		4,524
2013 Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	9,475	10,804
2014 Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	12,785	12,785
2015-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	3,985	3,985
2016-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	5,090	5,090
2017-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	6,085
2018-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	1,362
2014 Term Loan [Member]
Debt Instrument [Line Items]
Cash Interest	13,947	11,284
Non-cash Interest	131	128
2015 Term Loan [Member]
Debt Instrument [Line Items]
Cash Interest	4,697	3,800
Non-cash Interest	169	165
Other [Member]
Debt Instrument [Line Items]
Cash Interest	$ (151)	$ 13

Shareholders' Equity (Narrative

Shareholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	3 Months Ended
	Apr. 30, 2018	Mar. 31, 2018	May 07, 2018	Feb. 16, 2018
Stock Repurchase Program [Member]
Class of Stock [Line Items]
Stock repurchase program, authorized				$ 1,000
Stock Repurchase Program [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Stock repurchase program, remaining authorization			$ 700
Stock Repurchase Program [Member] | Class A Common Stock [Member]
Class of Stock [Line Items]
Stock repurchased, shares		0.2
Stock repurchased, value		$ 38.5
Weighted average price per share		$ 161.60
Stock Repurchase Program [Member] | Class A Common Stock [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Stock repurchased, shares	1.6
Stock repurchased, value	$ 261.5
Weighted average price per share	$ 164.82
Previous Stock Repurchase Program [Member]
Class of Stock [Line Items]
Stock repurchase program, remaining authorization				$ 150

Stock-Based Compensation (Narra

Stock-Based Compensation (Narrative) (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)$ / shares
Stock-Based Compensation [Abstract]
Weighted-average fair value of options granted | $ / shares	$ 32.98
Total intrinsic value for options exercised | $	$ 16.6

Stock-Based Compensation (Sched

Stock-Based Compensation (Schedule of Assumptions used to Estimate Fair Value of Stock Options) (Details)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock-Based Compensation [Abstract]
Risk free interest rate	2.57%	1.91%
Dividend yield	0.70%	0.00%
Expected volatility	22.00%	20.00%
Expected lives	4 years 7 months 6 days	4 years 7 months 6 days

Stock-Based Compensation (Summa

Stock-Based Compensation (Summary of Stock Option Activity) (Details) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)$ / sharesshares
Stock-Based Compensation [Abstract]
Number of Shares, Outstanding at December 31, 2017 | shares	4,842
Number of Shares, Granted | shares	922
Number of Shares, Exercised | shares	(180)
Number of Shares, Canceled | shares	(8)
Number of Shares,Outstanding at March 31, 2018 | shares	5,576
Number of Shares, Exercisable at March 31, 2018 | shares	2,883
Number of Shares, Unvested at March 31, 2018 | shares	2,693
Weighted-Average Exercise Price Per Share, Outstanding at December 31, 2017 | $ / shares	$ 100.12
Weighted-Average Exercise Price Per Share, Granted | $ / shares	156.52
Weighted-Average Exercise Price Per Share, Exercised | $ / shares	72.61
Weighted-Average Exercise Price Per Share, Canceled | $ / shares	109.13
Weighted-Average Exercise Price Per Share, Outstanding at March 31, 2018 | $ / shares	110.32
Weighted-Average Exercise Price Per Share, Exercisable at March 31, 2018 | $ / shares	95.84
Weighted-Average Exercise Price Per Share, Unvested at March 31, 2018 | $ / shares	$ 125.84
Weighted-Average Remaining Contractual Life (in years), Outstanding at March 31, 2018	4 years 7 months 6 days
Weighted-Average Remaining Contractual Life (in years), Exercisable at March 31, 2018	3 years 6 months
Weighted-Average Remaining Contractual Life (in years), Unvested at March 31, 2018	5 years 10 months 24 days
Aggregate Intrinsic Value, Outstanding at March 31, 2018 | $	$ 337,860
Aggregate Intrinsic Value, Exercisable at March 31, 2018 | $	216,484
Aggregate Intrinsic Value, Unvested at March 31, 2018 | $	$ 121,376

Stock-Based Compensation (Sum64

Stock-Based Compensation (Summary of Restricted Stock Unit Activity) (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Stock-Based Compensation [Abstract]
Number of Shares, Outstanding at December 31, 2017 | shares	328
Number of Shares, Granted | shares	128
Number of Shares, Vested | shares	(122)
Number of Shares, Forfeited/canceled | shares	(3)
Number of Shares, Outstanding at March 31, 2018 | shares	331
Weighted-Average Grant Date Fair Value per Share, Outstanding at December 31, 2017 | $ / shares	$ 110.20
Weighted-Average Grant Date Fair Value per Share, Granted | $ / shares	156.52
Weighted-Average Grant Date Fair Value per Share, Vested | $ / shares	110.61
Weighted-Average Grant Date Fair Value per Share, Forfeited/canceled | $ / shares	128.65
Weighted-Average Grant Date Fair Value per Share, Outstanding at March 31, 2018 | $ / shares	$ 127.83

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Billions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Income Taxes [Abstract]
Effective income tax rate	21.00%	35.00%
Net federal operating tax loss carry-forward		$ 1

Segment Data (Narrative) (Detai

Segment Data (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)segment	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
Segment Reporting Information [Line Items]
Number of business segments | segment	2
Number of reportable segments | segment	2
Site leasing	$ 430,542	$ 397,550
Total assets	7,405,082		$ 7,320,205
International Site Leasing [Member]
Segment Reporting Information [Line Items]
Total assets	2,133,870		2,028,479
Brazil [Member]
Segment Reporting Information [Line Items]
Site leasing	61,200	$ 53,200
Total assets	$ 1,262,500		$ 1,278,900

Segment Data (Segment Reporting

Segment Data (Segment Reporting Information Disclosure) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues		$ 458,302	$ 423,363
Cost of revenues		115,337	110,970
Operating profit		342,965	312,393
Selling, general, and administrative	[1]	36,049	34,223
Acquisition related adjustments and expenses		3,044	2,969
Asset impairment and decommission costs		8,506	8,351
Depreciation, amortization and accretion		165,398	159,031
Operating income		129,968	107,819
Other expense (principally interest expense and other income (expense))		(89,841)	(66,823)
Income before provision for income taxes		40,127	40,996
Cash capital expenditures		148,978	78,398
Assets		7,405,082		$ 7,320,205
Domestic Site Leasing [Member]
Segment Reporting Information [Line Items]
Revenues		341,707	321,130
Cost of revenues		65,015	65,427
Operating profit		276,692	255,703
Selling, general, and administrative		19,339	19,356
Acquisition related adjustments and expenses		1,786	1,901
Asset impairment and decommission costs		6,726	7,430
Depreciation, amortization and accretion		123,458	123,896
Operating income		125,383	103,120
Cash capital expenditures		71,019	50,433
Assets		5,139,407		5,171,190
International Site Leasing [Member]
Segment Reporting Information [Line Items]
Revenues		88,835	76,420
Cost of revenues		27,802	23,955
Operating profit		61,033	52,465
Selling, general, and administrative		6,614	5,959
Acquisition related adjustments and expenses		1,258	1,068
Asset impairment and decommission costs		1,502	816
Depreciation, amortization and accretion		39,680	32,825
Operating income		11,979	11,797
Cash capital expenditures		77,056	26,890
Assets		2,133,870		2,028,479
Site Development [Member]
Segment Reporting Information [Line Items]
Revenues		27,760	25,813
Cost of revenues		22,520	21,588
Operating profit		5,240	4,225
Selling, general, and administrative		4,077	3,617
Asset impairment and decommission costs		278	105
Depreciation, amortization and accretion		642	711
Operating income		243	(208)
Cash capital expenditures		267	133
Assets		53,144		49,487
Not Identified by Segment [Member]
Segment Reporting Information [Line Items]
Selling, general, and administrative		6,019	5,291
Depreciation, amortization and accretion		1,618	1,599
Operating income		(7,637)	(6,890)
Other expense (principally interest expense and other income (expense))		(89,841)	(66,823)
Cash capital expenditures		636	$ 942
Assets		$ 78,661		$ 71,049
[1]	Includes non-cash compensation of $9,893 and $8,826 for the three months ended March 31, 2018 and 2017, respectively.

Earnings Per Share (Narrative)

Earnings Per Share (Narrative) (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from earnings per share calculation	0.3	2.4

Earnings Per Share (Weighted-Av

Earnings Per Share (Weighted-Average Shares of Common Stock Outstanding used in Calculation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net income	$ 31,545	$ 37,598
Basic weighted-average shares outstanding	116,494	121,049
Dilutive impact of stock options and restricted shares	1,799	685
Diluted weighted-average shares outstanding	118,293	121,734
Net income per common share:
Basic	$ 0.27	$ 0.31
Diluted	$ 0.27	$ 0.31